DRIVING FORCE TRANSMISSION DEVICE OF AUTOMOBILE AND LOWER BODY STRUCTURE OF AUTOMOBILE INCLUDING THE SAME

PROBLEM TO BE SOLVED: To provide a driving force transmission device of an automobile and a lower body structure of the automobile including the same, allowing sufficiently obtaining of a buffer effect due to a collision by sufficiently securing rear displacement amount of a power unit in the collision in a vehicle longitudinal direction, while suppressing an increase of manufacturing cost.SOLUTION: This driving force transmission device includes the power unit 2, a rear differential device 3 and a propeller shaft 4 for transmitting driving force of the power unit 2 to the differential device 3. The propeller shaft 4 is divided into front and rear sides via a universal joint 43 and can be reduced by fitting the front divided shaft 4a together with at least a part of the universal joint 43 into an end part of the rear side divided shaft 4b over a reduction range D1. The rear differential device 3 includes a device body 31 and a rear side supporting part 33 for supporting the device body 31 so that a front part of the device body 31 may rotate downward. A retreating allowing space 1a is provided between the power unit 2 and a dash panel 10 on a horizontal rear side of the power unit 2.