A cork cap having a head and a leg and adapted to be inserted in a bottle mouth. A cork is press-fitted in the cap so that its bottom end protrudes from the bottom of the leg and is pressed against the inner surface of the bottle mouth to seal the bottle mouth. The cork can be pulled out by pulling the cork cap while twisting it. Protrusions are formed on the inner periphery of the tapered inner surface of the head between adjacent ones of a plurality of vertical ribs. The protrusions bite into the cork, thus keeping the cork strongly coupled to the cork cap even when the latter is pulled and twisted. Thus, the cork can be reliably pulled out together with the cork cap by twisting and pulling only the cork cap.