A fixing device having a rotatable heating member heated by a heat source, a rotatable pressure member for pressing against the rotatable heating member, a heat-moving member formed of material having excellent thermal conductivity characteristics and constructed so as to freely make contact with at least one rotatable member among the rotatable heating member and the rotatable pressure member, and a drive unit to move the heat-moving member between a contact position and retracted position relative to at least one of the heating member and the rotatable pressure member. The heat-moving member changes either heat capacity or thermal conductivity or both heat capacity and thermal conductivity relative to the axial direction of the rotatable heating member or the rotatable pressure member.