To provide a circuit breaker for preventing a load from being broken by incorrect wire connection.

The circuit breaker includes a high potential side power supply terminal 10H and a low potential side power supply terminal 10L which are respectively connected to the high potential side and the low potential side of a DC power supply, a pair of switching means 20 which are respectively inserted between the high potential side power supply terminal 10H and a load terminal 11H corresponding to the high potential side power supply terminal 10H and between the low potential side power supply terminal 10L and a load terminal 11L corresponding to the low potential side power supply terminal 10L, an incorrect connection detection means 3 which outputs a detection signal to show an incorrect connection when the polarity of the high potential side power supply terminal 10H and the polarity of the low potential side power supply terminal 10L is a reversed polarity, and a control means 4 which releases each of the pair of switching means 20 when the detection signal is input.