A step unit comprises: a step member which is provided on the vehicle body side so as to be adjacent to a slide door of the vehicle and has a flat plate section on which an occupant's foot is placed; and a drive device which is affixed to the step member and drives the slide door to open and close the slide door. The step member is molded using a resin material and has a accommodation portion which is provided with a bottom formed below the upper surface of the flat plate section. The drive device is affixed while at least a part thereof is accommodated within the accommodation portion.
