ELECTRICAL FAULT DETECTION DEVICE AND VEHICLE POWER SUPPLY SYSTEM

In electrical fault detection device (10) that is mounted on a vehicle and includes: energy storage unit (20) to be mounted in a state of being insulated from a chassis ground of the vehicle; first switch (MRp) inserted into positive wire (Lp); and second switch (MRm) inserted into negative wire (Lm), in order to suppress a total cost by not using an expensive component while securing detection accuracy, electrical fault detection device (10) further includes coupling capacitor (Cc), AC output unit (13a), first voltage measurement unit (13b), first determination unit (13c), voltage dividing circuit (11), second voltage measurement unit (12), and second determination unit (13d). Voltage dividing circuit (11) is connected between positive wire (Lp) between first switch (MRp) and one end of load (2) and negative wire (Lm) between second switch (MRm) and the other end of load (2).