It is intended to provide a method for producing an NK cell-enriched blood preparation, which is low invasive and is capable of conveniently and rapidly growing NK cells, etc. in blood collected from an organism. The NK cells in blood are stimulated with NK cell growth-stimulating factors comprising an anti-CD16 antibody, OK432, an anti-CD137 antibody, and a cytokine. Then, the blood is cultured at a physiological cell temperature to produce an NK cell-enriched blood preparation.
