Fixing device and image forming device

An image forming device, including at least a fixing device, said fixing device comprising:

• a heat transmitting unit, having a heating source;
• and
• a sheet unit, in contact with the heat transmitting unit, for applying a pressure, wherein one end of the sheet unit is fixed on an installation fitment arranged 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, and wherein 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, and
• wherein a length of the sheet unit in the recording paper transporting direction becomes shorter while approaching a central portion of the nip portion, and becomes longer than that at the two ends of the nip portion.