Abstract: A stopper is mounted on a vibrationproofing unit including a first bracket, a second bracket , an inside member being shaft shaped and in which the first bracket is fixed to the axial ends of the inside member, and a vibrationproofing base body including a rubber-like elastic body and coupling the outer circumferential face of the inside member and the inner circumferential face side of a tubular section of the second bracket. The stopper is plate shaped, includes a rubber-like elastic body, and includes a cushioning section disposed between the portions of the first bracket and the tubular section opposite in an axial direction of the tubular section. The cushioning section includes a thick wall section, a plurality of protrusion sections protruding from at least one face in a plate thickness direction of the thick wall section, and a thin wall section thinner than the thick wall section.