A differential pressure regulating valve is disposed in a fluid passage. The differential pressure regulating valve includes a valve chamber, a valve hole, a valve body, a support member and an urging member. The valve chamber is formed in the fluid passage and having a cylindrical shape. The valve hole is formed in the fluid passage as an opening which communicates with the valve chamber. The valve body is disposed in the valve chamber and adapted to open and close the valve hole. The support member is fixedly mounted to the valve chamber and extending across flowing direction of the fluid in the valve chamber. The support member has a communication passage for fluid communication between a first valve chamber and a second valve chamber. The urging member is disposed between the support member and the valve body for urging the valve body toward the valve hole.