To detect the occurrence of partial discharge of electric facilities/apparatus in a simple manner and to reliably determine/evaluate the occurrence of partial discharge while discriminating it from an environmental electromagnetic wave.

Only the electromagnetic wave having electromagnetic wave intensity in a board accommodating electric facilities/apparatus larger than that outside the board is detected as a partial discharge electromagnetic wave to determine/evaluate the partial discharge. The in-board electromagnetic wave detected within a specific phase range of a power supply voltage waveform of the electric facilities/apparatus is detected as the partial discharge. Further, the in-board electromagnetic wave having the timing the same as a ground current detection value generated in the electric facilities/apparatus is detected as the partial discharge. An absolute rectified waveform of the electromagnetic wave is subjected to envelope waveform processing and fast Fourier transform to determine/evaluate the occurrence of partial discharge on the basis of the value of the Fourier coefficient (signal intensity). The electromagnetic wave is detected in a field having no environmental electromagnetic wave. The antenna reception electromagnetic wave is detected by subjecting it to down-conversion processing into an intermediate frequency signal.