FIXING DEVICE

A fixing device includes a heat generating member extending in a longitudinal direction and having a first region and a second region, an endless belt, an opposing member opposing the endless belt, a heat conductive member extending in the longitudinal direction within the first region in which a surface of the heat conductive member contacts the heat generating member, a positioning portion extending from an end portion of the surface, an electric power shut-off member provided at a position corresponding to the second region, and a supporting member provided with an opening at a position corresponding to the second region and configured to support the heat generating member through the heat conductive member. The opening is configured to permit insertion of the positioning portion to prevent movement of the heat conductive member.