The functions of snake mobbing by Siberian chipmunks were studied in the context of potencial benefit to the mobbers themselves. In experiment I, the threatening effect of the mobbing was examined, and following results were obtained. The snake retreated almost always into a shelter box when it was mobbed, and the time span from the beginning of the mobbing until the completion of the snake's retreat into the box was shorter when the snake was mobbed by 2 chipmunks than when mobbed by a single one. These results indicate that mobbing has a threatening effect against the snake that increases when more chipmunks mob. In experiment II, I examined whether chipmunks get information about the snake during the mobbing. The experiment showed that the chipmunks performed tail shakings after the mobbing more frequently at large snakes than at small ones, and also indicated that mobbing functions to obtain useful information about snakes. This study clarified that the snake mobbing by Siberian chipmunks provides benefits to the mobbers themselves.