A shock absorber capable of suppressing load fluctuation after the start of plastic deformation. The shock absorber formed of a hollow molded body, including a load input surface; a fixed surface opposed to the load input surface; and a connection surface connecting the load input surface and the fixed surface. The connection surface includes at least one transverse groove rib, the at least one transverse groove rib includes at least two bending induction portions provided at positions where distances from the load input surface are different from each other, the at least two bending induction portions each being convex toward an outside of the shock absorber.