An airtight cap structure is provided, in which the number of parts is not increased, and moreover, a design property can be given, and air-tightness can be secured.A cap is configured by two-color molding of a soft portion comprised of an elastic soft resin, and a hard portion comprised of a hard resin, and in a state in which the cap is attached to a main body, the use end portion is inserted into the elastic soft portion to mare a direct contact to be sealed, and at the same time, the surface of the tip end portion of the main body is brought into contact with the soft portion, thereby securing air-tightness of a refill.