To alleviate injury of a chest part and a head part of an occupant due to bent deformation of a center pillar upon side collision by setting the bent deformation caused by bending stress of the center pillar to occur at a height position where sufficient cross section bending resistance to cross section bending input is obtained.

A reinforcement panel 3, a center pillar inner panel 4, two reinforcements 8, 9 disposed between the reinforcement panel and the center pillar inner panel are jointed with joint flanges 5, 7 at a vehicle front side and a vehicle rear side to form a closed section shape for the square-shaped center pillar 1. A position where a valley-folded ridge line RL1 at a bent section positioned in a vehicle outer side direction of the joint flange 7 placed on the rear side of the vehicle and a mountain-folded ridge line RL2 at a bent section positioned on a vehicle rear side of the reinforcement panel 3 and in a vehicle outer side direction is set lower than a belt line BL.