A fusing device includes a pressure member, a heating member, and an external heating member. The heating member has an outer surface in contact with an outer surface of the pressure member. The heating member heats a sheet that is being passed in a first direction through a contact area between the pressure member and the heating member. The external heating member heats a predetermined area of the surface of the heating member from outside. Length of the predetermined area along a second direction that is perpendicular to the first direction is set shorter than entire length of the heating member along the second direction.