It's the first conviction after three years of investigation, to determine whether several African leaders bought assets in France with embezzled state funds.
The corruption probe focused on Congolese President Denis Sassou Nguesso, late Gabonese president Omar Bongo Ondimba, and the Obiang family.
The conviction comes after French police seized properties and cars from Teodorin Obiang, who is renowned for living a lavish lifestyle.
French magistrates had issued an an international arrest warrant for him last year after he ignored a summons. But his lawyer, Emmanuel Marsigny, says his position as vice-president gives him immunity from being judged in a foreign country.
"We're going to file a lawsuit to challenge this conviction which violates internal law, because international law accords immunity to Heads of State and important dignataries," he said.
The government of Equatorial Guinea has called on France to drop its investigation of the Obiang family, cancel an arrest warrant against the President's son and return all seized property. Demands that have so far been ignored.