The Paris court found Teodorin Obiang, who is the country's vice-president, guilty of embezzlement, money laundering, corruption and breach of trust.
It gave the 48-year-old a three-month suspended sentence and a suspended fine of 30 million euros - both of which will come into effect if he reoffends in France.
Obiang did not attend the trial in June and July, describing it as a "farce".
His lawyers slammed an "activist decision" and said they were considering an appeal.
Bongo, Sassou Nguesso also targeted
Teodorin Obiang is the son of Equatorial Guinea's President Teodoro Obiang Nguema, who seized power from his uncle, Francisco Macias Nguema, in 1979.
He was named agriculture and forestries minister in 1997, before being promoted to vice-president in 2012.
A frequent visitor to France, where he attended a school in Normandy that specialises in educating foreign leaders' children, he bought a six-storey mansion near Paris's exclusive Champs Elysées avenue, a fleet of luxury cars, artworks and other assets, allegedly spending 1,000 times his official annual salary.
He paid for suits from Paris's top tailors with suitcases full of cash.
Many of the purchases were made through Somagui Forestal, a forestry company that prosecutors dubbed "an empty shell used solely to channel public money".
Bugattis, Ferraris, Rolls-Royce seized
Although Equatorial Guinea is one of Africa's top oil producers and exports timber from its rainforests, over half its population lives in less than 1.90 dollars (1.60 euros) a day.
In 2011 investigators raided Teodorin Obiang's Paris residence, hauling off Bugattis, Ferraris, a Rolls-Royce Phantom and other cars.
They seized the 4,000m² property, which is worth 107 million euros and has a hammam, a disco and gold-plated taps, the following year.
Claiming it is a diplomatic mission, Equatorial Guinea's government has appealed to the International Court of Justice.
The Hague-based court made an interim ruling in December 2016 that prevents France confiscating or auctioning it off until its status has been decided.
Failed coup leader testifies
The defence's accusation that France is meddling in the affairs of another country won support from a surprising source during the trial.
Former British mercenary Simon Mann, who led a failed coup attempt against Obiang Nguema in 2004, testified on behalf of the government, claiming that the case was the work of US billionaire George Soros.
Teodorin Obiang, who faces another corruption case in Switzerland, is head of broadcaster Asonga and plays a leading role in the Associaion of the Sons of Obiang, an organisation that promotes his father's reputation.
Transparency International, one of the NGOs involved in the case, has demanded that any money recovered from the sale of his assets be returned to Equatorial Guinea rather than being kept by the French state.