ELECTRICITY LEAKAGE DETECTION DEVICE AND VEHICLE POWER SUPPLY SYSTEM

In leakage detecting device (10) that detects an electric leakage from a high-voltage unit in which power storage unit (20) and a load are connected by a power supply line in a state of being insulated from an earth, Y capacitor (CY) is connected between the earth and a current path between power storage unit (20) and the load. Drive unit (11) of leakage detecting device (10) outputs a rectangular wave voltage to the current path between power storage unit (20) and the load via driving coupling capacitor (Cd1) to charge or discharge Y capacitor (CY). Leakage detector (12) determines presence or absence of the electric leakage between the current path and the earth according to a time transition in which the voltage at the measurement point of the current path changed according to charging or discharging of Y capacitor (CY) converges to an original voltage.