To maintain a stable control pressure without impairing responsiveness when operating oil is at a low temperature by a damper mechanism for preventing a rapid change of the control pressure provided in an external of a sleeve of a solenoid valve.

The solenoid valve 60 includes a cover 21 which is fit into an outer circumference of a housing 11, and is cramped and fixed on a shaft-like sleeve 24. A spool 27 is slidably inserted in the sleeve 24. A damper piston 62 is slidably inserted in a sleeve outer circumference part 61, and a damper stopper 64 is fixed oppositely to the damper piston 62. A spring member 65 is arranged between the damper piston 62 and the damper stopper 64, and the damper piston 62 is pressed by elastic repulsive force of the spring member 65. The damper mechanism is formed of the sleeve outer circumference part 61, the damper piston 62, the damper stopper 64, and the spring member 65.