A plug-in discharge detection unit includes two plugs of a cathode and an anode configured to allow insertion into respective two plug insertion holes of a plug socket. A discharge detection section configured to allow detection of a noise of discharge superimposed on a voltage or current, and an arithmetic section configured to allow determination of whether discharge has occurred based on the noise. The detection unit further includes a ground terminal electrically connected to a ground; at least one first switch electrically connected to a secondary side of the respective plug; and a current limiting resistor electrically connected to a secondary side of the first switch. The current limiting resistor has a secondary side electrically connected to the ground terminal, and the arithmetic section changes, if determining that discharge has occurred, the first switch from an open state to a closed state to pass an artificial leakage current with a current value in accordance with a resistance value of the current limiting resistor through the ground terminal.