The spokeswoman who made the announcement did not say why the Belarusian authorities demanded he leave the country.
But according to reports in the Belarusian media, ambassador Nicolas de Lacoste never met President Alexander Lukashenko to give him copies of his credentials.
France, like other EU countries, has not recognized the Belarusian strongman's claim to a sixth presidential term in disputed elections in August last year.
"The Belarusian foreign ministry demanded that the ambassador leave before October 18," an embassy spokeswoman told AFP Sunday.
"Ambassador Nicolas de Lacoste left Belarus today."
"He said goodbye to the staff of the embassy and recorded a video message to the Belarusian people, which will appear tomorrow morning on the embassy's website."
The European Union has imposed waves of sanctions on Lukashenko after the country erupted in historic protests against his rule.