An image forming apparatus is provided with a main body, an image forming assembly accommodated in the main body, a withdrawable unit accommodated in the main body in such a manner as to be withdrawable to the outside, a fixing unit for fixing a toner image to a recording sheet with heat from the heating member by conveying the recording sheet having the toner image transferred thereto while nipping it between a heating member and the pressure member, and a temperature raising device for raising the temperature of the heating member. The fixing unit is detachably mounted on the withdrawable unit. On the other hand, the temperature raising device includes a mounting portion different from that of the heating member, and is fixedly attached to the withdrawable unit and is kept attached to the withdrawable unit even if the fixing unit is separated from the withdrawable unit.