To prevent that an animal mark moves backward toward a skin in an insertion path, and to prevent the generation of inflammation in the buried portion.

A stopper 1 is disposed behind an animal mark inserted into the body of an animal to block out the insertion path 4, thereby fixing the animal mark at a prescribed burying site. An antibacterial medicine is simultaneously included in the stopper 1 to prevent the generation of inflammation such as suppuration around the animal mark 2.