A driving portion is configured to cause a driving force to move a spool in a first direction, and a bias unit is configured to cause a biasing force to bias the spool in a second direction in an axis direction. A part of a lock region is defined as a throttle region at which a flowing amount of working fluid flowing from a supply port to an introduction port is throttled. The throttle region is set to be located at a movable end position of the spool in the second direction to which the spool arrives when the driving force is not applied to the spool.