To provide a switching apparatus which can connect a power supply automatically to a related apparatus such as a peripheral apparatus, etc., for instance a CRT, when the power supply is connected to a main apparatus such as a personal computer.

This switching apparatus has a current/field detection means which is provided on a wiring between a main apparatus and a power supply, and detects a current flowing through the wiring, or a field formed by the current, and a changeover means which is provided on a wiring between an apparatus related to the main apparatus and the power supply, and closes or opens the wiring between the related apparatus and the power supply according to a detection result, supplied by the current/field detection means.