Abstract: A backrest mechanism for a stand-up rider operator's platform in an industrial vehicle, in which an operator operates the vehicle while standing, has a support portion and a support holder. The support portion has a backrest portion for supporting a back of the operator and a seat portion for at least supporting buttocks of the operator. The support portion supports the operator by either of the backrest portion and the seat portion. The support holder is located on a rear side of the vehicle from the operator's platform. The support holder holds the support portion so that the support portion is detachable from the support holder.