The present invention relates to a magnetic head actuator and a magnetic disk device in which a magnetic head is moved to a predetermined position by actuating an arm on a revolving magnetic disk. A magnetic head actuator comprises an arm in which a suspension for supporting a magnetic head is provided, the arm being actuated to move the magnetic head. A damper material is provided on at least one side of the arm, the damper material comprising a restriction material and a viscoelastic material, the restriction material suppressing vibrations of the arm, and the viscoelastic material absorbing vibrations of the arm.