Fixing device with decrease in sliding resistance of endless belt and frictional wearing thereof

A fixing device comprising a heat unit and a pressure unit, a toner image on a sheet being thermally fixed between the heat unit and the pressure unit, at least one of the heat unit and the pressure unit comprising:

• an endless belt having a width in a widthwise direction and extending in a circumferential direction perpendicular to the widthwise direction, the endless belt comprising:
• a base layer having an outer peripheral surface and a pair of widthwise end faces in the widthwise direction, the base layer defining an inner space;
• and
• an elastic layer formed on the outer peripheral surface and having a thickness and a pair of widthwise end surfaces in the widthwise direction, one of the end faces and a corresponding one of the end surfaces providing a maximum distance therebetween in the widthwise direction smaller than the thickness;
• a nip member provided in the inner space and configured to nip the endless belt in cooperation with a remaining one of the heat unit and the pressure unit;
• the one of the widthwise end surfaces having a portion positioned inside of the corresponding one of the end faces in the widthwise direction;
• and
• a restriction member positioned outside of each of the widthwise end faces in the widthwise direction, the restriction member being configured to be abutted against the widthwise end face.