A battery condition monitoring device has a control section for monitoring conditions of a high voltage battery on the basis of detection signals detected and transmitted by monitoring ICs. The control section has a main control section and a sub control section. When the main control section is in an abnormal condition, the sub control section detects the conditions of the high voltage battery, and instructs SMRs to turn on and off an electrical connection between the high voltage battery and a vehicle driving electric motor. The SMRs are arranged on connection lines through which the high voltage battery is connected to the vehicle driving electric motor.