An ESD protection circuit includes a power MOS transistor disposed between a first line and a second line, a clamp circuit disposed between the first line and a first node to which a gate of the power MOS transistor is coupled, a first resistor disposed between the first node and the second line, a MOS transistor disposed between the first node and the second line, a third line supplied with a third potential generated by a constant-voltage circuit of the protection target circuit, and a second resistor and a first capacitor coupled in series between a second node coupled to the third line and the second line, wherein when defining a junction between the second resistor and the first capacitor as a third node, a gate of the MOS transistor is coupled to the third node.