PURPOSE: To detect partial discharge generated in compressed gas insulation equipment at high sensitivity by providing a slit conductor, the insulating section of which can be adjusted in length, and a cover of a ferromagnetic substance to the insulating flange section of an insulating spacer.

CONSTITUTION: A slit 7a constituting a slit antenna for detecting a high frequency current caused by partial discharge is formed in the surrounding area of an insulating spacer 5 and a cover 7, the part of which farther from the slit 7a is constituted of a ferromagnetic substance 8, is fitted. As a result, the slit section of a slit conductor 9 surrounding the insulating flange section of the spacer 5 acts as a slit antenna, the resonance frequency of which can be changed by adjusting the width of the slit 7a. Therefore, an inexpensive partial discharge detecting device for compressed gas insulation equipment which can detect partial discharge generated in compressed gas insulation equipment at high sensitivity and has a simple constitution can be obtained.