Daniel Paillé's two-year stint as Bloc Québécois leader ended Monday when he announced his resignation because he has epilepsy.
"I am leaving for health reasons,'' Paille told a news conference in Montreal.
"I have been having health problems for the last few months and it turns out it is epilepsy.''
Paillé, 63, said he can no longer withstand the pace required to head a political party.
"Why now? Leading a political party requires that one must be in exceptional shape and have incredible endurance...I'm passing the torch. In the circumstances, this is the best time for the party.''
Paillé has been Bloc leader since December 2011 when he replaced Gilles Duceppe. The Bloc has only four of the province's 75 Commons seats.
Paillé was elected as an MP in a byelection in 2009 before being defeated in the 2011 general election.
He previously served as Quebec industry minister in the mid-1990s under the Parti Québécois.