INSULATION DETERIORATION MONITOR DEVICE

An insulation degradation monitoring device by which a degradation state of an insulator can be constantly monitored by a simple configuration, and a degradation degree can be decided. An insulation degradation monitoring device for an insulator (3), by which a high-voltage charging portion (1) of an electric instrument is insulated from and supported to a grounding metal component (2), comprises a penetration-type electric current sensor (6) which is inserted to a connecting portion of the insulator (3) and the grounding metal component (2), and detects a leakage electric current which is passed from the high-voltage charging portion (1) through the insulator (3) and is flowed to the grounding metal component (2); and a decision means (8) which is connected to an output side of the electric current sensor (6), and decides a degradation degree of the insulator 3() in accordance with a value of the leakage electric current.