To improve detection accuracy at a present position of a valve and durability of a valve position detection means by providing an immovable member near a moving coil or a valve with the valve position detection means for detecting these relative positions and measuring displacement of the valve.

An electromagnetic actuator is constituted with a permanent magnet 10 and a moving coil 13. Because a magnetic flux is generated in a clearance accommodating a bobbin 11b wound with the moving coil 13, when current is conducted to the moving coil 13, a force for axially moving a valve driving body 11 is applied to the body 11. An electrode 18 is mounted in an air feed hole 8 drilled through a yoke 7, and a small-diameter sensor shaft (iron core) 3d connected with a shaft portion 3a of a valve 3 is positioned in this electrode 18 in the non-contact state. An electrostatic-capacity-type valve- position detection means is constituted with these electrode 18 and the sensor shaft 3d, and relative position between the yoke 7, detects the sensor shaft 3d, and measures vertical displacement of the valve 3.