a heater including a substrate and a resistance heating element disposed on the substrate, the substrate including a first end and a second end in a longitudinal direction of the heater, the resistance heating element including a first end and a second end in the longitudinal direction, the first end of the resistance heating element being the nearest end of the resistance heating element to the first end of the substrate in the longitudinal direction, the second end of the resistance heating element being the nearest end of the resistance heating element to the second end of the substrate in the longitudinal direction;

an endless belt configured to rotate around the heater,

a first temperature sensor disposed at a position opposed to the heater and configured to detect a temperature at a center part of the heater in the longitudinal direction of the heater; and

a second temperature sensor disposed at a position opposed to the heater and configured to detect a temperature at an end part of the heater in the longitudinal direction of the heater, the second temperature sensor including a first end and a second end in the longitudinal direction,

wherein both of the first end and the second end of the second temperature sensor are located on an outer side of an area in which a maximum width of a largest possible sheet that can be used in the fixing device passes in the longitudinal direction of the heater, and

wherein both of the first end and the second end of the second temperature sensor are disposed at a position located between the first end of the substrate in the longitudinal direction of the heater and the first end of the resistance heating element in the longitudinal direction of the heater or a position located between the second end of the substrate in the longitudinal direction of the heater and the second end of the resistance heating element in the longitudinal direction of the heater.