PROBLEM TO BE SOLVED: To provide a plug body of a waterer for small animal which has excellent water tightness between a water supply cylinder and a container and facilitates engagement and separation of constituent members.SOLUTION: The plug body fixes a water supply cylinder to a container and is constituted by a cap and an elastic plug. The elastic plug includes: a through hole which is arranged at a center part and insertable with the water supply cylinder； plural annular crimps which are arranged on an outer peripheral surface and elastically contact an inner wall surface of an inlet part of the container； an annular flange engaged with the cap and a groove formed by the annular flange, arranged at a tip. A tip part of the cap is formed with: an annular projection part engaged with the groove of the elastic plug； and an inclined notch arranged at the annular projection part.
