A shock absorbing member to be arranged at a side end portion of a vehicle and formed into a tubular shape so as to extend in a vehicle front-and-rear direction, the shock absorbing member being deformable when a load is applied to a side portion of the vehicle, to thereby absorb shock caused by the load, the shock absorbing member comprising: an outer wall portion formed so as to extend in a vehicle height direction and the vehicle front-and-rear direction, and configured to be subjected to the load; an inner wall portion formed so as to extend in the vehicle height direction and the vehicle front-and-rear direction, and arranged on a center portion side of the vehicle in a vehicle width direction with respect to the outer wall portion so as to be opposed to the outer wall portion; an upper wall portion connected to an upper end portion of the inner wall portion and an upper end portion of the outer wall portion; a lower wall portion connected to a lower end portion of the inner wall portion and a lower end portion of the outer wall portion; and characterised in a horizontal rib formed in a space surrounded by the outer wall portion, the inner wall portion, the upper wall portion, and the lower wall portion, and connected to the inner wall portion and the outer wall portion, wherein a length of the outer wall portion in the vehicle height direction is set smaller than a length of the inner wall portion in the vehicle height direction, wherein a distance in the vehicle height direction between the upper wall portion and the lower wall portion becomes smaller as approaching from the inner wall portion side to the outer wall portion side, and wherein a thickness of a part of the horizontal rib, which is connected to the outer wall portion side, is set larger than a thickness of a part of the horizontal rib, which is connected to the inner wall portion side. an outer wall portion formed so as to extend in a vehicle height direction and the vehicle front-and-rear direction, and configured to be subjected to the load; an inner wall portion formed so as to extend in the vehicle height direction and the vehicle front-and-rear direction, and arranged on a center portion side of the vehicle in a vehicle width direction with respect to the outer wall portion so as to be opposed to the outer wall portion; an upper wall portion connected to an upper end portion of the inner wall portion and an upper end portion of the outer wall portion; a lower wall portion connected to a lower end portion of the inner wall portion and a lower end portion of the outer wall portion; and characterised in a horizontal rib formed in a space surrounded by the outer wall portion, the inner wall portion, the upper wall portion, and the lower wall portion, and connected to the inner wall portion and the outer wall portion, wherein a length of the outer wall portion in the vehicle height direction is set smaller than a length of the inner wall portion in the vehicle height direction, wherein a distance in the vehicle height direction between the upper wall portion and the lower wall portion becomes smaller as approaching from the inner wall portion side to the outer wall portion side, and wherein a thickness of a part of the horizontal rib, which is connected to the outer wall portion side, is set larger than a thickness of a part of the horizontal rib, which is connected to the inner wall portion side.