An apparatus includes groove-shaped thin portions, of which the length direction is in a vertical direction, that are provided at predetermined intervals in the front-back direction in front of a hip point of a seat side garnish. When an impacting body impacts the seat side garnish and a load is applied to the seat side garnish, first, stress concentrates at the thin portions, and then the area between the thin portion and the thin portion of the seat side garnish, and the area between the thin portion and the thin portion of the seat side garnish deforms so as to move inward in the vehicle width direction. As a result, the seat cushion will readily rise up in front of the hip point, and is thus able to be prevented or suppressed from rising up at the hip point.