Here is the gross debt of every country as percentage of GDP for 2017 (source: International Monetary Fund),
All countries have at least some gross debt and 10 countries have no net debt.
Japan has both the highest gross and net debt as percentage of GDP.
Here is the data set (negative values for net debt as % of GDP indicate that the country has no debt); G20 countries are highlighted in bold,
(Country; Gross debt as percentage of GDP; Net debt as percentage of GDP)
Afghanistan; 7.346; N/A
Albania; 71.244; 65.472
Algeria; 25.802; 20.487
Angola; 65.266; N/A
Antigua and Barbuda; 86.823; N/A
Argentina; 52.615; N/A
Armenia; 53.467; N/A
Australia; 41.592; 19.094
Austria; 78.833; 54.32
Azerbaijan; 54.702; N/A
The Bahamas; 57.205; N/A
Bahrain; 90.335; N/A
Bangladesh; 32.414; N/A
Barbados; 132.876; 76.284
Belarus; 50.962; N/A
Belgium; 103.184; 90.324
Belize; 99.023; N/A
Benin; 54.597; N/A
Bhutan; 102.398; N/A
Bolivia; 50.86; 35.369
Bosnia and Herzegovina; 40.972; 33.735
Botswana; 15.646; -2.683
Brazil; 83.98; 51.583
Brunei Darussalam; 2.689; N/A
Bulgaria; 23.927; 10.878
Burkina Faso; 38.327; N/A
Burundi; 56.69; N/A
Cabo Verde; 126.029; 116.538
Cambodia; 35.134; N/A
Cameroon; 33.832; 30.418
Canada; 89.688; 27.793
Central African Republic; 53.441; N/A
Chad; 52.533; N/A
Chile; 23.593; 5.257
China; 47.79; N/A
Colombia; 49.414; 41.27
Comoros; 28.381; N/A
Democratic Republic of the Congo; 15.664; N/A
Republic of Congo; 119.073; N/A
Costa Rica; 49.098; N/A
Côte d’Ivoire; 46.391; N/A
Croatia; 78.414; N/A
Cyprus; 99.258; N/A
Czech Republic; 34.663; 22.869
Denmark; 36.413; 16.273
Djibouti; 30.649; 28.101
Dominica; 87.57; N/A
Dominican Republic; 37.743; 28.556
Ecuador; 44.979; N/A
Egypt; 103.261; 94.005
El Salvador; 59.319; N/A
Equatorial Guinea; 42.676; N/A
Eritrea; 131.244; N/A
Estonia; 8.772; -0.572
Ethiopia; 56.223; 52.228
Fiji; 46.623; 42.332
Finland; 61.369; 22.574
France; 96.956; 87.651
Gabon; 61.065; N/A
The Gambia; 123.239; N/A
Georgia; 44.918; N/A
Germany; 64.137; 45.099
Ghana; 71.839; 65.273
Greece; 181.906; N/A
Grenada; 71.448; N/A
Guatemala; 24.375; N/A
Guinea; 39.669; N/A
Guinea-Bissau; 41.971; N/A
Guyana; 50.676; 50.676
Haiti; 31.087; N/A
Honduras; 43.949; N/A
Hong Kong SAR; 0.055; N/A
Hungary; 69.906; 66.413
Iceland; 40.906; 33.344
India; 70.2; N/A
Indonesia; 28.913; 24.802
Islamic Republic of Iran; 40.866; 29.741
Iraq; 57.98; N/A
Ireland; 68.52; 59.829
Israel; 60.971; 57.928
Italy; 131.454; 119.885
Jamaica; 104.074; N/A
Japan; 236.388; 153.04
Jordan; 95.557; 88.489
Kazakhstan; 21.184; -11.784
Kenya; 55.646; 50.364
Kiribati; 26.315; N/A
Korea (Republic of); 39.782; 6.609
Kosovo; 20.94; N/A
Kuwait; 20.641; N/A
Kyrgyz Republic; 59.092; N/A
Lao P.D.R.; 62.769; N/A
Latvia; 34.835; 26.918
Lebanon; 152.846; 147.164
Lesotho; 34.703; -0.944
Liberia; 34.434; 31.997
Libya; N/A; N/A
Lithuania; 36.52; 29.717
Luxembourg; 23.032; -8.284
Macao SAR; 0; N/A
FYR Macedonia; 39.254; 38.446
Madagascar; 37.276; N/A
Malawi; 59.318; N/A
Malaysia; 54.157; N/A
Maldives; 68.051; N/A
Mali; 35.557; 29.866
Malta; 52.622; N/A
Marshall Islands; 27.969; N/A
Mauritania; 91.086; 90.799
Mauritius; 60.15; N/A
Mexico; 54.181; 46.12
Micronesia; 24.489; N/A
Moldova; 37.72; N/A
Mongolia; N/A; N/A
Montenegro; 67.493; N/A
Morocco; 64.407; 64.042
Mozambique; 102.243; N/A
Myanmar; 34.725; N/A
Namibia; 46.103; 43.643
Nauru; 60.147; N/A
Nepal; 27.15; N/A
Netherlands; 56.658; 46.173
New Zealand; 26.428; 4.649
Nicaragua; 33.562; N/A
Niger; 46.528; 40.894
Nigeria; 23.401; 19.608
Norway; 36.655; -90.469
Oman; 44.22; -10.776
Pakistan; 67.173; 61.608
Palau; N/A; N/A
Panama; 38.158; 35.881
Papua New Guinea; 32.609; N/A
Paraguay; 25.566; 20.437
Peru; 25.507; 10.118
Philippines; 37.825; N/A
Poland; 51.382; 46.668
Portugal; 125.619; 108.098
Puerto Rico; 54.573; N/A
Qatar; 53.962; N/A
Romania; 36.878; 28.341
Russia; 17.437; N/A
Rwanda; 40.599; N/A
Samoa; 49.121; N/A
San Marino; 56.569; N/A
São Tomé and Príncipe; 83.3; N/A
Saudi Arabia; 17.289; -7.723
Senegal; 61.152; N/A
Serbia; 61.476; 58.684
Seychelles; 63.315; 48.427
Sierra Leone; 58.428; N/A
Singapore; 110.864; N/A
Slovak Republic; 50.427; N/A
Slovenia; 75.367; N/A
Solomon Islands; 10.011; -1.101
Somalia; N/A; N/A
South Africa; 52.673; 47.896
South Sudan; 66.341; N/A
Spain; 98.364; 86.344
Sri Lanka; 79.424; N/A
St. Kitts and Nevis; 62.378; N/A
St. Lucia; 71.262; N/A
St. Vincent and the Grenadines; 80.813; 77.86
Sudan; 126.022; N/A
Suriname; 72.053; N/A
Swaziland; 29.173; 23.673
Sweden; 40.943; 9.014
Switzerland; 42.779; 23.053
Syria; N/A; N/A
Taiwan Province of China; 35.172; 33.291
Tajikistan; 47.784; N/A
Tanzania; 38.243; N/A
Thailand; 41.882; N/A
Timor-Leste; N/A; N/A
Togo; 78.633; N/A
Tonga; N/A; N/A
Trinidad and Tobago; 41.34; -10.968
Tunisia; 71.275; 21.269
Turkey; 28.482; 22.736
Turkmenistan; 28.82; N/A
Tuvalu; 49.186; N/A
Uganda; 38.955; N/A
Ukraine; 75.602; N/A
United Arab Emirates; 19.471; N/A
United Kingdom; 87.029; 78.166
United States; 107.785; 82.268
Uruguay; 66.19; 32.3
Uzbekistan; 24.539; N/A
Vanuatu; 48.412; N/A
Venezuela; 34.866; N/A
Vietnam; 58.231; N/A
Yemen; 141.014; 139.372
Zambia; 62.209; 56.349
Zimbabwe; 78.36; N/A
General government gross debt (Percent of GDP)
Gross debt consists of all liabilities that require payment or payments of interest and/or principal by the debtor to the creditor at a date or dates in the future. This includes debt liabilities in the form of SDRs, currency and deposits, debt securities, loans, insurance, pensions and standardized guarantee schemes, and other accounts payable. Thus, all liabilities in the GFSM 2001 system are debt, except for equity and investment fund shares and financial derivatives and employee stock options. Debt can be valued at current market, nominal, or face values.
General government net debt (Percent of GDP)
Net debt is calculated as gross debt minus financial assets corresponding to debt instruments. These financial assets are: monetary gold and SDRs, currency and deposits, debt securities, loans, insurance, pension, and standardized guarantee schemes, and other accounts receivable.