A pressure regulating valve includes a device body and an actuator. The device body includes a valve seat member, a valve, which is capable of closing the first opening of the valve seat member, an urging member, which urges the valve toward the valve seat member, a piston arranged opposite to the valve across the valve seat member, an actuator, which adjusts the position of the piston, and a protrusion provided on at least one of the piston and the valve. When the tip end of the protrusion comes into contact with the piston or the valve, the second opening of the second fluid passage is closed. When the tip end of the protrusion is not in contact with any of the piston and the valve and the second opening is opened, the second fluid passage is in communication with the pressure regulation chamber.