A judge convicted Carlos Fabra on four counts of tax evasion but acquitted him of charges of accepting bribes and influence-peddling, the court in the eastern province of Castellon said in a written ruling.
Fabra was the leader of Prime Minister Mariano Rajoy's conservative Popular Party in Castellón, part of Valencia, a region now synonymous with claims of political corruption during the Spanish building boom that went bust in 2008.
As president of the Castellón provincial council, Fabra oversaw controversial public spending projects such as the building of an airport which is now derelict and seen as a symbol of bad investments in the boom.
A colourful character who wears dark sunglasses at all times in public, Fabra stood trial last month along with four other defendants including his wife, Amparo Fernandez.
The trial followed a 10-year investigation into alleged financial irregularities, including tax evasion from 1999 to 2003.
The court ordered Fabra to pay a fine of €693,000 ($935,000) and also to pay the same amount to the taxman. It also sentenced Fernandez to two years' jail for tax evasion.
It acquitted Fabra of charges of accepting commissions for awarding public contracts.