HEATER, AND IMAGE FORMING APPARATUS

A heater includes: a substrate; a heating element, provided on a first surface of the substrate and extending in a longitudinal direction of the substrate; a protection part, provided on the first surface, extending in the longitudinal direction of the substrate, and covering the heating element; and at least one relaxation part, provided on a second surface of the substrate facing the first surface. A coefficient of thermal expansion of the protection part and a coefficient of thermal expansion of the at least one relaxation part are different from a coefficient of thermal expansion of the substrate. A material of the at least one relaxation part is the same as a material of the protection part, or a main component of the material of the at least one relaxation part is the same as a main component of the material of the protection part.