An electric leak detector (108) for a vehicle includes a coupling capacitor (210) that has a terminal (A) connected to an on-vehicle high voltage device (110) and a terminal (B) connected to a repetitive signal output circuit (212). The coupling capacitor (210) repeatedly performs a charge operation and a discharge operation in response to a repetitive signal (PLS). Determination thresholds are calculated based on a voltage applied to the terminal (A) of the coupling capacitor (210) and an atmospheric temperature. A detected charge period and a detected discharge period are compared with the determination thresholds, to thereby determine a leakage state.