A seat device for use in a vehicle that can move through an opening of a vehicle between a loading and unloading position positioned outside the vehicle, where a passenger can load and unload as well as be seated, and a seating position positioned in the cabin of the vehicle, where the passenger can maintain a seated disposition. A securing member of the seat device can secure a wheelchair in a folded state to a side surface or a back surface of the seat. The wheelchair together with the seat can move from the loading and unloading position to inside the cabin of the vehicle, with the passenger in a seated position.
