Provided is a switching device allowing power to be stably supplied and interrupted, and limits the effects of chattering due to a mechanical relay when the mechanical relay is combined with a solid state relay, and when the supply and interruption of the power is performed. The switching device comprises: a semiconductor relay for switching between supplying and interrupting the power from a power source; a mechanical relay connected in parallel to the semiconductor relay and where one extremity is connected to a control terminal of the semiconductor relay; and a switch for switching between supplying and interrupting the current to the semiconductor relay. The semiconductor relay is brought into an ON state when allowing a high-state voltage to be applied to the control terminal after switching contacts where a current circulates into a coil of the mechanical relay. The semiconductor relay is brought into an OFF state when allowing a low-state voltage to be applied to the control terminal after switching the contacts where a current circulating into the coil of the mechanical relay is interrupted.