To provide the structure of a facility behind a driving seat in a wheelchair moving vehicle with which the rate of utilization of a transportation vehicle is maximally improved by securing the maximum seating capacity and also to provide a slide seat device to be used for the structure.

The structure includes a foldable seat device 14 to be moved selectively to a seat position S where the device 14 faces an internal wall forming a rear space 91 arranged behind the driving seat, etc., and a footrest gap 101 for allowing a person to sit down by expanding a seat 141 is formed when moving backward most or to a position T where the device 14 is stored by being arranged tightly close or adjacent to the internal wall by folding the seat 141 into a backrest 140 when moving forward most. Besides operability is enhanced by moving the foldable seat device by sliding. Thus, the seat is easily moved in a small place and an internal space is effectively utilized.