To reduce the amount applied as energy to a rear frame structure by increasing the energy absorption in a body front in every collision mode.

A front side member 1 is hollowly formed of a member body 11 and a closing plate 13, and a reinforcing member 39 is housed in the hollow front side member 1. The reinforcing member 39 is fixed to the member body 11 through connecting flanges 51, 53, and 55 in the rear end thereof. In a full- flap collision, the front side member 1 is compressed and deformed, but the deformation is not extended to the reinforcing member 39. In an offset collision, the front side member 1 is compressed and deformed more than in the full-flap collision, and the reinforcing member 39 is also compressed and deformed to absorb the impact.