A secondary battery protection circuit includes a first terminal connected to a power supply path between a secondary battery and a MOS transistor, a second terminal connected to the power supply path between a load and the MOS transistor, a third terminal connected to a gate of the MOS transistor, a fourth terminal connected to a back gate of the MOS transistor, a control circuit that outputs a switch control signal based on a detected abnormal state of the secondary battery, and a switch control circuit including a first switch for connecting the fourth terminal with the first terminal and a second switch for connecting the fourth terminal with the second terminal. At least one of the resistance between the fourth terminal and the first terminal and the resistance between the fourth terminal and the second terminal is greater than the on resistance value of the MOS transistor.