In an indoor structure of a vehicle including a door (12) provided in a door opening (20) at the side of a vehicle and a step (5) for passenger ingress and egress provided on the indoor side of the door opening, the step being located at a lower position than a floor (4) of the vehicle compartment, an expanded floor portion (6) substantially level with the floor (4) is provided on the vehicle rear side of the step (5). Also, a rear leg (24) of a foldable seat (2) is extended outward in the vehicle width direction in the vehicle compartment, and is placed on the expanded floor portion (6).