An object is to provide an electromagnetic actuator that is highly resistant to corrosion and also capable of having high suction power, even in a condition where part of the electromagnetic actuator touches a corrosive liquid. An electromagnetic actuator 50 according to this invention is incorporated into a device using a corrosive liquid 17. The electromagnetic actuator 50 is characterized by including a magnetic pole piece 1; an outer yoke 6; a bottom yoke 5; a bobbin coil 2; a stepped portion 6a that is formed on an outer surface of the outer yoke 6; a waterproof portion 8 that prevents the corrosive liquid 17 from entering at least where the bobbin coil 2 and the magnetic pole piece 1 are; a movable plate 12 that is placed in the corrosive liquid 17 to form a magnetic circuit together with the magnetic pole piece 1, the outer yoke 6, and the bottom yoke 5, The movable plate 12 is stored in a space 14 created either in the electromagnetic actuator 50 or between the device using the corrosive liquid 17 and the electromagnetic actuator 50. The outer yoke 6 is incorporated into the device using the corrosive liquid 17, on a reduced diameter side from the stepped portion 6a.