The growth, faster than expected, was pulled by household spending and gross fixed capital formation, statisticians said. Analysts in a CTK poll predicted 5.7 percent growth on average.
Household spending on final consumption grew by 6.5 percent year-on-year in real terms and by 8.6 percent or Kc32.6 billion in current prices, beating the disposable income growth slightly.
The categories of cars, food, tobacco, furniture and recreation showed the highest nominal increases in spending.
In current prices, GDP grew by 10.2 percent to Kc899.7 billion in the second quarter. Total gross added value rose to Kc813 billion. The difference is formed by taxes on products, above all excise tax and VAT, less subsidies.
The year-on-year growth in added value was pulled by the processing industry, car sales and repairs, and services for companies.
Gross fixed capital formation grew by 4.2 percent in real terms year-on-year on investment in buildings and non-housing construction, which swallowed 41 percent of total investment in gross fixed capital.
The contribution of individual spending items to GDP growth varied.
Spending on household consumption and gross fixed capital formation grew, while foreign trade had a negligible impact and a drop in spending on final consumption by institutions in the government sector was a negative influence.
Statisticians also revised indicators for the first quarter, raising the original GDP growth estimate from 6.1 to 6.4 percent.
GDP in EU-27 countries grew by an estimated 2.8 percent year-on-year in the second quarter, said the EU's statistical office Eurostat. Euro zone GDP grew by 2.5 percent.
GDP in Slovakia grew by 9.4 percent, in Poland by 6.9 percent, in Austria by 3.7 percent, in Germany by 2.5 percent and in Hungary by 1.8 percent in the second quarter.