Abstract: A solenoid valve includes a valve seat with a hole, a magnetically conductive hollow winding reel, an induction coil unit wound around the reel, a permanent magnet fixed on the reel, and a magnetically insulating vertical tube disposed within the reel. A moving core is biased by a spring to a lower limit position so as to close the hole, thereby preventing water flow though the hole. A magnetic fluid is filled within a sealed gap between the reel and the tube. When a forward current flows through the coil unit, the core is attracted by the magnet so as to move to an upper limit position, where the hole is open, thereby permitting the water flow through the hole. When the core is disposed at the upper limit position and when a reverse current flows through the coil unit, a magnetic repulsion force is created between the magnet and the core, thereby returning the core to the lower limit position with assistance from the spring.