PURPOSE: To prevent the deformation of a fixing belt for preventing a failure in fixing and an offset and simultaneously, to easily remove the paper sheet jammed in a pressure roller part by releasing the pressure of the pressure roller of a fixing device, in a state where a device is not used.

CONSTITUTION: The pressurizing lever 53 imparting prescribed pressure to the roller 25 for pressurizing a transfer material on a heating element 21a and a releasing lever 57 releasing the pressurizing force of the pressurizing lever 53 are provided. The releasing lever 57 is supported so as to vertically slide on a front side plate 51 by a stepped screw 66 attached thereto and fitted into an oblong hole 57b provided on the releasing lever 57. Then, the releasing lever 57 is pulled upward (a releasing position side) by the taut force of a releasing spring 64 extended between the top end of the lever 57 and an immobile part, in the state where the transfer material is not made to pass. Thus, the pressurization of the pressure roller 25 on the heating element 21a is released. The value of the taut force of the releasing spring 64 is set larger than that of a pressurizing spring 55.