The utility model discloses embodiment provides an insulating defect detecting device for current transformer, and insulating defect detecting device includes: the quantum sensor sets up near currenttransformer, laser generator for to the lasing of quantum sensor with the excitation quantum sensor, the microwave transceiver for to quantum sensor transmitting microwave signal and receive the microwave signal of quantum sensor feedback, the electron spin resonance spectroscopy appearance for start laser generator obtained current transformer with the microwave transceiver and according to the microwave signal that feeds back electric field and/or the distribution characteristics of of magnetic field intensity on the space, the treater for judge according to the electric field that detects out and/or magnetic field intensity's distribution characteristics of whether current transformer exists the defect and judging the defect type who confirms this defect under the condition that there is the defect in current transformer. This insulation defect detecting device can be to current transformer's electric field, the defect type that the magnetic field distribution characteristic detected and judged this current transformer.