An opening degree adjustment device for a vehicle door includes a door check including a pressing member and being fixed to a vehicle door mounted to a vehicle body; a check link including a sliding surface to be pressed by the pressing member, one end being supported on the vehicle body so as to be pivotable, and another end having a stopper member mounted thereon, the check link being movable relative to the door check within a predetermined movable range of the check link between the one end of the check link and the another end of the check link under a state in which the sliding surface is pressed by the pressing member, and an opening degree adjustment block including a first checking region configured to restrict movement of the stopper member.