A mobile object is configured so as to be capable of moving front and rear bases 10,30 object to each other in order to make a wheel base provided between the front wheels 12 and the rear wheels 32 expandable and contractible. The front base 10 moves so as to be expand and contract the tread width between the front wheels 12 in association with the expansion and the contraction of the wheel base achieved. The seating part 41 is configured so as to turn forward in association with the relative movement of the front and rear bases 10,30 in order to contract the wheel base and the tread width. The seating part 41 is configured so as to turn backward in association with the relative movement of the front and rear bases 10,30 in order to expand the wheel base and the tread width.
