To provide a differential heat sensor capable of preventing individual differences in contact interval by preventing individual differences in the bending angle of a plate spring that forms a contact mechanism.

The differential heat sensor is formed by the plate spring in which one of a moving-contact spring 10 and a fixed-contact spring 11 is formed flatly in its longitudinal direction, the plate spring being secured to a sensor body 5 at one end by a securement part and attached to the sensor body 5 while being bent at a predetermined angle to a diaphragm 8 as it is pressed toward the diaphragm 8 by a pressing portion 15 provided to protrude from the sensor body 5 toward the diaphragm 8.