A bottom lid (54) of a bottle cap is molded integrally at a lower end of an inner tubular portion of a cap body (A) with a cut (54a) formed therebetween and has unsealing projections (66) formed in a projecting manner thereon. When the cap body (A) is turned in a sealing direction to insert the inner tubular portion into a mouth (50a) of a bottle (50), the unsealing projections (66) are closed by the bottle mouth (50a) and are engaged with a throat portion (50c) in the bottle (50) when it passes the throat portion (50c). Then, when the cap body (A) is turned in an unsealing direction to pull out the inner tubular portion from the bottle mouth (50a), the unsealing projections (66) are blocked from upward movement by the throat portion (50c), whereupon the bottom lid (54) is separated at the cut (54a) from the lower end of the inner tubular portion and raw material (C) in the inner tubular portion is discharged into the bottle (50).