A solenoid valve useful in a slip-controlled hydraulic brake system of a motor vehicle, and which has a seat valve disposed between a pressure fluid inlet and a pressure fluid outlet and in the bypass to the seat valve has a check valve with a quad ring as a closing body and a circular ring surface as a valve seat. Circularly disposed pressure fluid openings adjoin the circular ring surface and are overlapped on the radial inside and on the radial outside by respective sealing lips of the annular rubber-elastic closing body, which is guided with axial motion play in relation to the circular ring surface.