A walk-substituting vehicle includes a foldable chassis, a steering mechanism, a seat assembly, and a fixing device, which is movable to a fastening portion to prevent the chassis from folding from an in-use position; the chassis includes a main part and a footrest part; the vehicle can be moved to a folded configuration, wherein the chassis is folded, and the steering mechanism and the seat assembly lie on the chassis; the fixing device includes a pulling member pivoted on the footrest part, a joining member pivoted on the pulling member, and a pushing member joined on and slideable along a receiving recessed portion of the pulling member; when the fixing device is in the fastening position, the joining member will be hooked over the main part of the chassis, and the pushing member engaged with the joining member to prevent the joining member from pivoting relative to the pulling member.