To provide a flow passage switching device and a flow passage switching method of wash water for a bidet simplified in manufacturing process by simplifying an assembling process, while reducing manufacturing cost by reducing the number of parts required for constituting the flow passage switching device.

This flow passage switching device of the wash water for the bidet includes at least one water inlet formed at the outer peripheral surface one side and making the wash water flow in, a water outlet making the wash water flowing in the water inlet port flow out, a flow passage switching valve including an air inflow port formed at the front tail end, an inflow pipe for storing the flow passage switching valve and formed in a position coincident with the water inlet, a valve housing including at least one nozzle connecting pipe formed in a position coincident with the water outlet, a motor installed at the rear side tail end of the flow passage switching valve and rotating the flow passage switching valve, and an air pump for mixing air in the air inflow port.