A fixing device including a heat transmitting unit and a sheet unit. The heat transmitting unit has a heating source, which can be for example disposed inside the heat transmitting unit. The sheet unit is in contact with the heat transmitting unit for applying a pressure against the heat transmitting unit. One end of the sheet unit is fixed on an installation fitment that is arrange at an upstream side of a transporting direction of a recording paper with respect to the heat transmitting unit, and the other end of the sheet unit is pressed to be in contact with the heat transmitting unit. Furthermore, when the recording paper, where a toner image has been transferred thereon, passes through a nip portion between the heat transmitting unit and the sheet unit, the toner image is fixed by pressing and heating onto the recording paper.