To provide a cap for a lemon pop bottle which can be easily removed from a bottle mouth after drinking, can surely seal the bottle mouth before the drinking, and gives consideration to environmental issues.

This cap for the lemon pop bottle is composed of an inside stopper 13 and an outside stopper 14, by which a sphere 12 is held. A mouth-part engaging piece 15, which is equipped with a weakened part 17 composed of a vertical slit or a thin-walled part, is formed all around a lower part of the outside stopper 14. A cylindrical body 18, whose upper part is coupled with the outside stopper 14 via easy-to-cut parts such as a plurality of bridges 19, is provided on an outer periphery of the engaging piece 15; and the engaging piece 15 is prevented from being opened by internal pressure. After the drinking, when the cylindrical body 18 is circumferentially separated from the outside stopper 14, the engaging piece 15 is opened so that the whole cap can be easily removed from the mouth part 10.