FAILURE DIAGNOSTIC DEVICE

The present invention addresses the problem of diagnosing a failure of a discharge resistor, while suppressing deterioration of discharge capacity. Disclosed is a failure diagnostic device for a discharge circuit for discharging electricity from an electricity storage element The discharge circuit includes a resistance circuit comprising a plurality of resistor blocks B connected in parallel, and each of the resistor blocks B comprises a plurality of discharge resistors Ra, Rb connected in series. During the time when electricity is being discharged from the electricity storage element the failure diagnostic device diagnosis a failure of the resistance circuit on the basis of a voltage or a current at a connection point P between the discharge resistors Ra, Rb.