An operating device of a footstool which is adjustable the height is provided to reduce the whole thickness of the operating device and size of a motor. An operating device of a footstool which is adjustable the height comprises the followings: a rotatable male screw member(12) in the center part of a lower plate(2); a moving body(13) moving to a straight line according to a rotating of the male screw member; an operating body(14) moving with the moving body; two rollers(15) moving to up and down by an incline plane of the operating body; and two operating links(16) adhering to a hook of the operating body and rotating on the central axis.
