A solenoid valve includes a main valve configured to change a communication opening degree between a first port and a second port, a control pressure chamber configured to bias the main valve in a valve closing direction, an auxiliary valve configured to open and close a first communication passage and a second communication passage formed in the main valve, a solenoid portion configured to displace the auxiliary valve, a back pressure chamber and a sub-return spring configured to bias the auxiliary valve in a valve closing direction, and a pressure compensation unit configured to change a biasing force of the sub-return spring acting on the auxiliary valve according to a pressure in the back pressure chamber.