A solenoid valve includes a water inlet valve seat, a guide seat, a coil barrel, and a water outlet valve seat. When in an open state, an iron core is moved to close a pressure relief hole via an iron core spring and water pressure, and the diaphragm blocks the water flow of a water inlet via water pressure and the force of a guide spring, so as to achieve a bistable effect. The coil barrel includes two pairs of magnets and a pair of magnetically conductive sheets to form two magnetic routes. The solenoid valve has a simple structure and can be produced easily.