The case against Teodorin Obiang is part of a broader investigation into money laundering, also targeting the families of Gabon's late president, Omar Bongo, and Republic of Congo President Denis Sassou Nguesso.
France's top court on Tuesday rejected a request by the son of Equatorial Guinea's president to drop a formal investigation against him for suspected money laundering.
Teodorin Obiang, the son of President Teodoro Obiang, had appealed for charges against him to be dropped on grounds of diplomatic immunity, but the Cour de Cassation court ruled the charges relate "exclusively to his private life in France" and not to his official functions.
Obiang is second vice president of the small central African state, where a majority of the population lives in poverty despite rich oil reserves. He also faces money-laundering charges in the United States.
His lawyer was not immediately available for comment.
Obiang has denied wrongdoing and has said his wealth, which has allowed him to buy luxury real estate in Paris, a private jet and a stable of exotic sports cars, was amassed legitimately through successful business dealings.
The court also rejected Obiang's request to disqualify anti-corruption group Transparency International France as a party in the case. TI France filed a complaint against him and three other African heads of state and their entourages in 2008.
"There is no longer any obstacle in the way of starting the lawsuit now," TI France lawyer William Bourdon said.
The case against Teodorin Obiang is part of a broader investigation into money laundering, also targeting the families of Gabon's late president, Omar Bongo, and Republic of Congo President Denis Sassou Nguesso. Together they are suspected of owning 63 luxury properties in Paris and some 200 bank accounts.
In September, French judges ordered the seizure of a property tied to the family of Sassou Nguesso in an investigation over suspected ill-gotten wealth.
The presidents deny any wrongdoing, and Sassou Nguesso told the French courts in 2013 not to intervene in his country's internal affairs.