A method for protecting an occupant seated on a seat of a vehicle in a side collision of the vehicle is disclosed. In the method, the lumbar region of the occupant is retained in a section that corresponds to the pelvis rearward of the acetabulum in the skeletal structure of the occupant by using an impact absorbing member. Specifically, the lumbar region of the occupant is retained in a section that corresponds to an ilium in the skeletal structure of the occupant. In a side collision of the vehicle, the impact absorbing member initially contacts the lumbar region in a section corresponding to the ilium.