NOVELTY - The apparatus has insulation resistance measurement units (110,120) that are connected to anode and cathode terminals of a battery (10) through switches (SW1, SW2). The insulation detection voltage of battery from measurement units are transmitted to a voltage detecting portion (130). The voltage detecting portion is connected to a control unit (140). The control unit provided to determine malfunctioning of measurement unit based on the insulation detection voltages of battery, when voltage detecting portion is operated at malfunction self-diagnosis mode.    USE - Apparatus for measuring insulation resistance of battery e.g. secondary battery such as lithium ion battery, lithium polymer battery, nickel cadmium battery, nickel-hydrogen electric battery and nickel zinc battery used in mobile apparatus, uninterruptible power supply system, power storage system, electric vehicle, hybrid vehicle and battery power supplying system.    ADVANTAGE - The occurrence of malfunction in insulation resistance measurement apparatus can be self-diagnosed effectively, since control unit provided to determine malfunctioning of measurement unit based on the insulation detection voltages of battery, when voltage detecting portion is operated at malfunction self-diagnosis mode. The insulation resistance of battery can be measured efficiently. The number of components in insulation resistance measurement apparatus can be reduced. The fault information of insulation resistance measurement apparatus can be transmitted easily to the controller through the transmit unit. The fault information of insulation resistance measurement apparatus can be informed to the user. The discomfort of user can be prevented. The occurrence of flicker noise from drive motor can be prevented.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for a method for self-diagnosing occurrence of malfunction in insulation resistance measurement apparatus.    DESCRIPTION OF DRAWING(S) - The drawing shows a circuit diagram of the apparatus for measuring insulation resistance of battery. (Drawing includes non-English language text)    Battery (10)    Insulation resistance measurement unit (110,120)    Voltage detecting portion (130)    Control unit (140)    Switch (SW1-SW4)