A solenoid includes: a movable core configured to move in a first space of a main body case in an axial direction to apply a biasing force to a spool; a fixed magnetic pole portion configured to attract the movable core in the axial direction; an adjusting spring configured to apply the biasing force to the movable core; a biasing force adjusting member provided at an opening end portion of a rear case and configured to adjust an axial position thereof to adjust the biasing force; and a degassing plug provided at an opening end portion of the adjusting member and including a degassing passage that allows a second space to communicate with an outside by changing relative positions of the adjusting member and the degassing plug. A sealing portion configured to open or close communication between degassing passages is provided between the adjusting member and the degassing plug.