To provide a half drink cap for a beverage container which can correspond to a plurality of beverage containers having different port diameters of port bases and can prevent an insect and dust from entering and mingling.

The half drink cap for a beverage container includes a first tapered part which corresponds to the port diameter of a drinking port of a PET bottle and is formed integrally such that the port diameter increases outward and downward from an outer edge of a top plate part, and a second tapered part which corresponds to the port diameter of a first beverage container having a port base larger than the drinking port of the PET bottle and is provided integrally more outward and downward than the first tapered part. The first tapered part and the top plate part constitute a pull-top stay-on-tab housing in an upward convex shape which can be housed with a pull-top stay-on-tab erected.