A fuser includes a fixing belt that is endless and includes a heat generating layer and circulates, an end restraining member that supports an end of the fixing belt, a heat generating source that is disposed around the fixing belt and heats the heat generating layer, an opposite part that contacts an outer peripheral surface of the fixing belt, a pressure part that is disposed inside the fixing belt and located at a position opposite to the opposite part, and presses the fixing belt to the opposite part side to form a nip between the fixing belt and the opposite part, and a rotation part that contacts an inner peripheral surface of the fixing belt at a position opposite to the heat generating source.