To prevent a position, where an occupant took his seat, from being shifted when a vehicle travels, improving his seating comfortability, and to lessen any required force at a time when the occupant goes on board of the vehicle.

This vehicular getting in/out device 1 is equipped with a gangway supporting member 2 being detachably installed in and around a sheet cushion 5 in a vehicle 4, and also equipped with a gangway 3 mounted so as to be laid over space between an upper end 2d of this gangway supporting member 2 and a top face of the seat cushion 5, and further a recess 3a is installed in a part corresponding to the upper end 2d of the gangway supporting member 2. Thus this boarding and alighting device 1 is composed of installing a through port, wherein the recess 3a is detachably engaged, in the upper end 2d of the gangway supporting member 2.