Abstract: A sealing structure for a fitting portion where an annular member is concentrically fitted to a cylindrical member to be fitted at a cylindrical part of the annular member is disclosed. The sealing structure is characterized by an elastic annular seal layer integrally provided on the backward end part of the annular member or the cylindrical member in fitting direction, by applying elastomeric agent to the backward end part and hardening it, and the elastic annular seal layer is formed such that it has layer thickness of 5 ?m to 1 mm and is interposed in a compressed state between the annular member and the cylindrical member when said annular member is fitted to said cylindrical member.