A leakage detecting device configured to detect an electric leakage from a high-voltage unit in which a power storage unit and a load are connected by a power supply line (Lp, Lm) in a state of being insulated from an earth, and comprise a Y capacitor (CY) connected between (i) a current path between the power storage unit and the load and (ii) the earth; wherein the leakage detecting device comprises: a driving coupling capacitor (Cd1); a drive unit configured to output a rectangular wave voltage to the current path between the power storage unit and the load via the driving coupling capacitor (Cd1) to charge or discharge the Y capacitor (CY); and a leakage detector configured to determine whether a leakage occurs between the current path and the earth, characterized by a measurement coupling capacitor (Cd2), wherein the leakage detector is configured to determine whether the leakage occurs between the current path and the earth according to a time transition in which a voltage at a measurement point of the current path changed according to charging or discharging of the Y capacitor (CY) converges to an original voltage, and the leakage detector is configured to measure the voltage at the measurement point of the current path via the measurement coupling capacitor (Cd2). a Y capacitor (CY) connected between (i) a current path between the power storage unit and the load and (ii) the earth; wherein the leakage detecting device comprises: a driving coupling capacitor (Cd1); a drive unit configured to output a rectangular wave voltage to the current path between the power storage unit and the load via the driving coupling capacitor (Cd1) to charge or discharge the Y capacitor (CY); and a leakage detector configured to determine whether a leakage occurs between the current path and the earth, characterized by a measurement coupling capacitor (Cd2), wherein the leakage detector is configured to determine whether the leakage occurs between the current path and the earth according to a time transition in which a voltage at a measurement point of the current path changed according to charging or discharging of the Y capacitor (CY) converges to an original voltage, and the leakage detector is configured to measure the voltage at the measurement point of the current path via the measurement coupling capacitor (Cd2). a driving coupling capacitor (Cd1); a drive unit configured to output a rectangular wave voltage to the current path between the power storage unit and the load via the driving coupling capacitor (Cd1) to charge or discharge the Y capacitor (CY); and a leakage detector configured to determine whether a leakage occurs between the current path and the earth, characterized by a measurement coupling capacitor (Cd2), wherein the leakage detector is configured to determine whether the leakage occurs between the current path and the earth according to a time transition in which a voltage at a measurement point of the current path changed according to charging or discharging of the Y capacitor (CY) converges to an original voltage, and the leakage detector is configured to measure the voltage at the measurement point of the current path via the measurement coupling capacitor (Cd2). <EOS>