PURPOSE: To enhance the effect of lay-out in the interior of a passenger compartment of an automobile of front-engine and front-drive type, by projecting the front side panel surface of the floor panel of the passenger compartment upward with respect to the rear side panel surface so that a storage space is obtained below the front side panel surface and the rear side panel surface is made to be a flat surface having a uniform height.

CONSTITUTION: In a small size passenger car of front-engine and front-drive type, etc., a fuel tank 11 and a spare tire storing space 40 are obtained below the front side 4a of a floor panel which is projected upward so that the level of the front side is higher by one step than the rear side 4b of the floor panel 4. Further, the front side 4a is connected with a front seat attachment member 6 which consists of a surmounting wall part 61 and an attachment wall part 62 and is attached with a front seat, and under which a hollow space S is formed. Meanwhile, the rear side 4b is made to be a flat surface having a uniform height, and is disposed thereon with a rear seat 7 in the middle section thereof with a luggage space being obtained in the rear of the rear seat 7. Further, the rear seat 7 is composed of two cushion members 71a, 71b, etc., which are foldable and unfoldable, thereby both passengers at the front and rear seats 5, 7 may simultaneously lay.