A valve includes: a valve housing provided with a primary pressure port and a secondary pressure port; a valve body configured to be driven by a solenoid; a valve seat on which the valve body is seated; and a spring that urges the valve body in a valve opening direction. The valve seat includes a first valve seat and a second valve seat disposed on a radially inner side of the first valve seat. The second valve seat is configured for moving in a direction toward the valve body due to a differential pressure between a primary pressure and a secondary pressure.