The present invention relates to a composition for preventing or treating cancer diseases, comprising IL-2 or an expression promoter or activator thereof as an active ingredient. In the present invention, it has been found that when IL-2 is applied to cancer cells, IL-2 inhibits secretion of exosomes derived from cancer cells and inhibits expression of PD-L1 that induces immune escape of T cells, thereby enhancing an anticancer effect. In contrast to conventional techniques that exhibit immune anti-cancer effects by activating cytotoxic T cells, IL-2 has also been found to have an anti-cancer effect directly on cancer cells. Therefore, IL-2 or an expression promoter or activator thereof can be advantageously used in a composition for preventing or treating cancer diseases.
