According to the present disclosure, a fixing device includes a heating member, a rotatable pressure roller, and a metal pattern. The heating member includes a heating rotary body configured to be heated by a heating device. The pressure roller is pressed against an outer circumferential surface of the heating rotary body. The metal pattern is disposed facing the heating member so as to extend in a sheet width direction which is equal to an axial direction of the pressure roller, and the metal pattern is formed of a metal wire of which a resistance varies according to variations in temperature of the heating member.