To provide a body structure for an automobile capable of easily obtaining a suitable habitability and a space for a baggage.

This body structure for an automobile comprises a front floor 11 of a low stage and a rear floor 15 of a high stage behind the front floor 11, and front rail 31 and a rear rail 35 are arranged on the front floor 11 and the rear floor 15 respectively. The body structure is provided with a slide deck 40 which is movable along the front rail 31 and the rear rail 35 and moves between on the rear floor 15 and above the front floor 11; and a rear seat 60 having a seat cushion 61 of which a front end is rockably supported at a front end of the slide deck 40 and a back rest capable of folding down on an upper surface of the seat cushion 61.