To effectively absorb a collision load of a power unit retracting with a front collision of a vehicle.

A reinforcing frame 27 of a hollow cross section disposed in a vehicle body fore-and-aft direction in a floor tunnel 20 is united to fore-and-aft frames 12, 13, 31 extending in the vehicle body fore-and-aft direction through cross members 15, 16 extending in a vehicle width direction. A front end 27a of the reinforcing frame 27 is made to face a rear surface of a power unit P. The reinforcing frame 27 pushed by the power unit P retracting with impact of vehicle collision retracts, so that the collision load of the vehicle is dispersed from the reinforcing frame 27 into the fore-and-aft frames 12, 13, 31 through the cross members 15, 16 and can be effectively absorbed. The reinforcing frame 27 with the hollow cross section has light weight, but is hard to buckle to a compressed load in an axial direction, so that the collision load can be effectively transmitted from the reinforcing frame 27 to the fore-and-aft frames 12, 13, 31.