An active vibration damper having: an electromagnetic oscillator with a coil member and a yoke member, one of the coil member and yoke member of the electromagnetic oscillator being fixed to a target member whose vibration to be damped while the other being elastically supported by the target member via a support rubber elastic body; and a base member having a cylindrical peripheral wall portion and a floor portion, and fixed to the target member. The support rubber elastic body is housed within the base member, and the electromagnetic oscillator is disposed outside of the base member, on an opposite side of the support rubber elastic body with the floor portion of the base member being interposed. An insertion hole is formed at the floor portion of the base member, and the other of the coil and yoke member forms a coupling rod inserted through the insertion hole and fixed to a center portion of the support rubber elastic body.