The Paris Appellate Court has struck down Russian national Alexander Vinnik's appeal and ruled to keep him in custody.
Vinnik has been in France since January 23, after having been extradited from Greece.
Earlier, it was reported that Vinnik was finishing his 40-day hunger strike and returning to normal eating.
Vinnik was detained in Greece in July 2017 at the request of the US authorities on various charges, including laundering $4 billion through bitcoin cryptocurrency exchange BTC-E, which he allegedly ran as the head operator.
Vinnik has asked to be extradited to Russia to stand trial in his home country.