An energy absorber is formed of a fiber reinforced composite into a cylinder having a plurality of portions so that the thickness of the body gradually increases in at least two stages in the axial direction. Reinforcing fiber is wound around at least in a circumferential direction of the body and is impregnated with a resin. The body of the energy absorber has a thin portion continuous to a first end. The end surface of the first end has an area equal to or smaller than 2/3 of the cross-sectional area of the thin portion the vicinity of the junction between the thin portion and the portion adjacent which is thicker than that thin portion. That cross-sectional area of the thin portion continuously increases to the middle of the thin portion from the first end side. The energy absorber is used in a state where impact is applied from the axial direction of the body.
