An electromagnetic actuator for an active vibration isolation system, the electromagnetic actuator includes: a fixed core; a movable core that is opposed to the fixed core and is joined to a vibration member; and a coil unit having coils that surround part of the fixed core and the movable core. The movable core and the vibration member are vibrated in a reciprocating manner by energization to the coils, and the coils include a main coil to which an alternating current with a waveform corresponding to vibrations of a vibration generation source is input and a sub-coil that amplifies magnetic flux generated by the main coil.