Provided is an overheat protection circuit with improved accuracy of overheat detection. The overheat protection circuit includes: an input terminal; an output terminal; a first transistor containing a first terminal, a second terminal, and a control terminal, the first transistor being switchable between ON and OFF; and a first NPN transistor containing a base to be connected to a node between the second terminal of the first transistor and the ground terminal, an emitter to be connected to the ground terminal, and a collector to be supplied with a constant current and connected to the output terminal, the first NPN transistor being switchable between ON and OFF in accordance with a voltage level of a reference voltage to be supplied to the base, the reference voltage having a temperature characteristic of having a temperature coefficient of zero or more.