A protection circuit that includes a first power supply system including a first power supply and a first ground, a second power supply system including a second power supply and a second ground, the second power supply system being connected to the first power supply system via a signal line through which signal transfer is performed between a circuit in the first power supply system and a circuit in the second power supply system, and a control circuit that, when coupled to an electro-static discharge (ESD) stress being applied to the first power supply system controls a switch, the switch being provided between the signal line and the first power supply.