To provide an effective carcinostatic therapy reducing the side-effects of a carcinostatic agent, eliminating the load of a user and scarcely causing the generation of resistant cancer cells.

It is confirmed that the injection of the Bacillus natto inhibits the proliferation of cancer cells, controls the actions of the cancer cells and kills the cancer cells. When a cancer is metastasized through a lymph, the Bacillus natto further expresses the same phenomenon at the metastasized site. The carcinostatic action therapy using the Bacillus natto thereby exhibits a therapeutic effect sufficient for efficiently showing the action activity.