Electromagnetic actuator (1) comprises a plunger (11a, 11b) of the sensor magnet (21a, 21b) which are disposed in association with each of which is disposed at a position where the magnetic flux of the plurality of sensor magnet (21a, 21b) to flow and magnetic sensor core (22), varies according to the position of the sensor core (22) in a plurality of sensor magnet (21a, 21b) are installed in the portion where the magnetic flux can flow in common a plurality of plungers (11a, 11b) and a magnetic sensor (23) for detecting the magnetic flux.