It is intended to provide a method for producing an NK cell-enriched blood product, the method being less invasive and 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, a bisphosphonate derivative or a salt thereof, or a hydrate thereof, and a cytokine. Then, the blood is cultured at a physiological cell temperature to produce an NK cell-enriched blood product.
