Fixing device and image forming apparatus

A fixing device comprising:

• a fixing belt which is formed in a cylindrical shape and heats toner on a medium while rotating around an axis;
• a pressure member which forms a pressure region between the fixing belt and the pressure member, and pressurizes the toner on the medium passing through the pressure region while rotating around an axis;
• a heater which is in contact with an inner surface of the fixing belt in the pressure region and heats the fixing belt;
• and
• a heat source temperature detection member which detects a temperature of the heater, wherein
• the heater include:
• a substrate extending in an axial direction of the axis of the fixing belt, and
• a heat generating part which is formed at a position shifted in one direction from a center in the axial direction on one surface of the substrate facing the pressure region, and generates heat when being powered,
• the heater is divided into a short region having a shorter length in the axial direction and a long region having a longer length in the axial direction by the center of the heat generating part in the axial direction as a boundary, and
• the heat source temperature detection member is disposed in the short region of the heater.