To discriminate service interruption after an earthquake from usual service interruption, and prevent operation in usual service interruption by connecting a memory whose memory is not erased even if power is not supplied to a sensor to a CPU, and sending sense current to a main earth leakage breaker without using a battery in power recovering to break the main earth leakage breaker.

An arithmetic processor in a CPU 10 always monitors signals from an earthquake sensitive sensor 3 and a primary line 2, a computing result of the CPU 10 is stored in a memory 11 having a nonerasable function and making use of a battery unnecessary. Only when the earthquake sensitive sensor 3 senses the vibration of a set earthquake intensity or higher, a power signal from the primary line 2 is once cut and the power signal is inputted again, sensitivity current 8 is supplied to a main earth leakage breaker to break the main earth leakage breaker. By this constitution, the main earth leakage breaker cannot be operated in usual service interruption.