A flow rate control valve includes a coil disposed in a first body, a movable iron core axially displaceable under a magnetically exciting action of the coil, a fixed iron core fixed in the first body, a fluid supply port supplied with a fluid, a fluid discharge port discharging the fluid, a projection formed for a diaphragm which is connected to the movable iron core and which is formed of an elastic member, a valve seat for the projection to be inserted therein, and a spring which urges the movable iron core to separate from the fixed iron core in a non-excited state.