A cask comprising: a main body; a lid; and a cask cushioning body attached to both ends of the cask for absorbing an impact applied to the cask, wherein the cask cushioning body comprising: an end-surface side member in which a plurality of plates (21, 22) made of steel are formed at a distance between plate surfaces of the plates (21, 22) that face each other, and in which the plate surfaces of the plates (21, 22) are arranged along an end surface of the cask; and a circumferential-surface side member that forms a cylindrical body made of the steel, one end of which is connected to a periphery of the end-surface side member, and that is arranged along an end-portion outer-circumferential surface of the cask, wherein an impact absorber that absorbs the impact by deforming is provided outside of the end-surface side member and the circumferential-surface side member, wherein the cask cushioning body is configured so that a size between an outer circumferential surface of the lid of the cask and an inner circumferential surface of the circumferential-surface side member is larger than a size between an outer circumferential surface of the main body of the cask to which the lid is fixed and the inner circumferential surface of the circumferential-surface side member, characterized in that the cylindrical body includes a stepped portion formed by a recess at a portion facing the outer circumferential surface of the lid such that the stepped portion is made thinner than another portion facing the outer circumferential surface of the main body. a main body; a lid; and a cask cushioning body attached to both ends of the cask for absorbing an impact applied to the cask, wherein the cask cushioning body comprising: an end-surface side member in which a plurality of plates (21, 22) made of steel are formed at a distance between plate surfaces of the plates (21, 22) that face each other, and in which the plate surfaces of the plates (21, 22) are arranged along an end surface of the cask; and a circumferential-surface side member that forms a cylindrical body made of the steel, one end of which is connected to a periphery of the end-surface side member, and that is arranged along an end-portion outer-circumferential surface of the cask, wherein an impact absorber that absorbs the impact by deforming is provided outside of the end-surface side member and the circumferential-surface side member, wherein the cask cushioning body is configured so that a size between an outer circumferential surface of the lid of the cask and an inner circumferential surface of the circumferential-surface side member is larger than a size between an outer circumferential surface of the main body of the cask to which the lid is fixed and the inner circumferential surface of the circumferential-surface side member, characterized in that the cylindrical body includes a stepped portion formed by a recess at a portion facing the outer circumferential surface of the lid such that the stepped portion is made thinner than another portion facing the outer circumferential surface of the main body. an end-surface side member in which a plurality of plates (21, 22) made of steel are formed at a distance between plate surfaces of the plates (21, 22) that face each other, and in which the plate surfaces of the plates (21, 22) are arranged along an end surface of the cask; and a circumferential-surface side member that forms a cylindrical body made of the steel, one end of which is connected to a periphery of the end-surface side member, and that is arranged along an end-portion outer-circumferential surface of the cask, wherein an impact absorber that absorbs the impact by deforming is provided outside of the end-surface side member and the circumferential-surface side member, wherein the cask cushioning body is configured so that a size between an outer circumferential surface of the lid of the cask and an inner circumferential surface of the circumferential-surface side member is larger than a size between an outer circumferential surface of the main body of the cask to which the lid is fixed and the inner circumferential surface of the circumferential-surface side member, characterized in that the cylindrical body includes a stepped portion formed by a recess at a portion facing the outer circumferential surface of the lid such that the stepped portion is made thinner than another portion facing the outer circumferential surface of the main body.