A phase sequence switching device for a three-phase power supply is disposed in a power feed path from a three-phase power supply to a load and includes a power-supply side relay including two Form C contact relays connected to two phases of the power supply respectively, a load side relay including two Form C contact relays connected between the power-supply side relay and the load, and a switching circuit connected between the power-supply side relay and the load side relay and wired to be capable of switching by a relay action from a standby state where no power is supplied to the load to either a state where the power supply is connected to a positive phase so that power is supplied to the load side or a state where the power supply is connected to a reverse phase so that power is supplied to the load side.