<p>Provided is a shock absorber comprising a cylindrical small-diameter section, a cylindrical large-diameter section, and an annular stepped section which connects the small-diameter section and the large-diameter section. The shock absorber absorbs shock energy by absorbing an applied load by means of plastic deformation in which the small-diameter section is turned back at the annular stepped section into the large-diameter section. The large-diameter section is provided with protrusions extending in the axial direction and protruding outward in the radial direction. The shock absorber is configured so that the turning deformation occurs more stably, and as a result, the shock absorber can efficiently absorb shock energy. A bumper device for a vehicle is also provided.</p>
