<p>Provided is an electrical leak detection device galvanically isolating a battery from a vehicle body and accurately detecting the degradation of an insulating resistance. A battery pack (106) isolated from the vehicle body has an assembled battery (102) to which a primary winding (109) is connected in parallel. A current detection circuit (116) is configured by having: an ammeter-side secondary winding (113) transformer-coupled to the primary winding (109); an AC power supply (114) connected to the ammeter-side secondary winding (113) in series; and an ammeter (115) connected between the vehicle body and the AC power supply (114). The ammeter (115) detects leak current by supplying AC current from the current source (114) to the ammeter-side secondary winding (113). As described above, the battery pack (106) and the current detection circuit (116) connected to the vehicle body are galvanically isolated from each other by using a transformer.</p>
