Disclosed is an isolation resistance measuring apparatus having a fault self-diagnosing function. The isolation resistance measuring apparatus having a fault self-diagnosing function forms a diagnosis circuit by means of a first isolation resistance measuring unit and a second isolation resistance measuring unit respectively connected to a cathode terminal and an anode terminal of a battery, and includes a control unit for determining whether a fault arises at the isolation resistance measuring apparatus by using a circuit equation derived from the diagnosis circuit and first and second diagnosis voltages. Therefore, the isolation resistance measuring apparatus may diagnose whether a fault arises at a device which measures isolation resistance of a battery.