A fixing device includes: a first fixing member and a second fixing member forming a nip portion for heat-fixing a recording sheet; an urging mechanism including an urging member and urging the first fixing member toward the second fixing member by an urging force of the urging member; a first frame for supporting the second fixing member; a second frame arranged at an opposite side to the second fixing member with the first fixing member being interposed therebetween; and a switching member, which applies a pressing force resisting the urging force to the first fixing member for switching a width of the nip portion, and which includes a cam to which the urging force is applied and a shaft for supporting the cam. The first frame and the second frame are connected to each other by the shaft.