A station building power supply device includes a circuit breaker to disconnect a connection with a train side, a circuit breaker to disconnect a connection with the station load side, a power converter disposed between the circuit breaker and the circuit breaker to convert the regenerative power into the AC power, a housing that houses the circuit breaker, the power converter, and the circuit breaker, a voltage sensor that detects a charged state of the housing, and a control unit that controls operations of the circuit breaker, of the power converter, and of the circuit breaker based on a detection result from the voltage sensor.