In an interview given to the newspaper Uutispäivä Demari, he said the surplus could be as much as three billion euros.
Heinäluoma says it will be used to speed up repayments of the country's debt.
The unforseen development is due, says the Finance Minister, to a better-than-anticipated growth in tax revenue as well as cost-cutting measures.
Original forecasts predicted a budget deficit in the order of half a million euros.
Finnish News Agency, YLE24