A fixing device of belt fixing type is provided. A heat generating member that is a heat generating source for heating a fixing belt has a heat generating layer composed of a resistance heat generating element that generates heat due to being energized. The resistance heat generating element includes a paper passing region heating section and a detecting section provided on an end portion in an axial direction of the heat generating member and electrically connected in parallel with the paper passing region heating section. Furthermore, in a vicinity of the detecting section, an overheat preventing element that suppresses energization to the resistance heat generating element when temperature of the detecting section reaches a predetermined value, is provided.