An oil control valve has a cup shaft and a plunger. The cup shaft and the plunger have a projection and a recess to provide a male-female joint. The male-female joint provides contact points which can reduce lateral offset and inclination. The projection and the recess provides two or more force transmitting points from the plunger to the cup shaft, when the projection and the recess are inclined with each other. The force transmitting points are located about the central axis of the spool in a distributed manner.