Disclosed herein is a leakage detector provided in a device having a conversion circuit that converts a DC voltage and an AC voltage from one to the other and a grounded metal member. The leakage detector comprises: an average voltage detection circuit that detects the average voltage of voltages corresponding to a potential difference between a high-voltage-side terminal or a low-voltage-side terminal on the DC side of the conversion circuit and the metal member; and a leakage detection circuit that detects the presence/absence of a leakage based on the average voltage detected by the average voltage detection circuit.