A sealing device for sealing an annular space formed by a plurality of members (100, 110), comprising: a reinforcing ring having an annular shape around an axis (x); and an elastic body part formed from an elastic body, the elastic body part being attached to the reinforcing ring and having an annular shape around the axis, wherein: the elastic body part includes a seal lip that is an annular portion projecting toward one side in a direction of the axis, a secondary lip portion that is an annular portion projecting toward another side in the direction of the axis, and an outer peripheral portion that is a portion covering the reinforcing ring from an outer periphery side; the seal lip projects beyond the reinforcing ring toward the one side in the direction of the axis; and the secondary lip portion projects beyond the reinforcing ring toward the other side in the direction of the axis, characterized in that, in the outer peripheral portion, a plurality of identification parts are formed further on the one side or the other side than a middle of the outer peripheral portion in the direction of the axis, the plurality of identification parts acting as marks, wherein the plurality of identification parts are recessed parts or protruding parts projecting from a surface of the outer peripheral portion, and provided at intervals around the axis a reinforcing ring having an annular shape around an axis (x); and an elastic body part formed from an elastic body, the elastic body part being attached to the reinforcing ring and having an annular shape around the axis, wherein: the elastic body part includes a seal lip that is an annular portion projecting toward one side in a direction of the axis, a secondary lip portion that is an annular portion projecting toward another side in the direction of the axis, and an outer peripheral portion that is a portion covering the reinforcing ring from an outer periphery side; the seal lip projects beyond the reinforcing ring toward the one side in the direction of the axis; and the secondary lip portion projects beyond the reinforcing ring toward the other side in the direction of the axis, characterized in that, in the outer peripheral portion, a plurality of identification parts are formed further on the one side or the other side than a middle of the outer peripheral portion in the direction of the axis, the plurality of identification parts acting as marks, wherein the plurality of identification parts are recessed parts or protruding parts projecting from a surface of the outer peripheral portion, and provided at intervals around the axis the elastic body part includes a seal lip that is an annular portion projecting toward one side in a direction of the axis, a secondary lip portion that is an annular portion projecting toward another side in the direction of the axis, and an outer peripheral portion that is a portion covering the reinforcing ring from an outer periphery side; the seal lip projects beyond the reinforcing ring toward the one side in the direction of the axis; and the secondary lip portion projects beyond the reinforcing ring toward the other side in the direction of the axis, characterized in that, in the outer peripheral portion, a plurality of identification parts are formed further on the one side or the other side than a middle of the outer peripheral portion in the direction of the axis, the plurality of identification parts acting as marks, wherein the plurality of identification parts are recessed parts or protruding parts projecting from a surface of the outer peripheral portion, and provided at intervals around the axis