This invention provides a method for producing NK cells from undifferentiated stem cells without using feeder cells in serum-free culture medium. [Solution] A method for producing NK cells without using feeder cells, comprising culturing undifferentiated stem cells in a serum-
free medium containing BMP4 and a GSK-3 inhibitor to form embryoid bodies, culturing them in a serum-
free medium containing VEGF, SCF, and a TGF-β inhibitor, culturing them in a serum-
free medium without a TGF-β inhibitor containing VEGF and SCF to differentiate them into
hematopoietic progenitor cells, culturing them in a serum-free medium containing IL-7, SCF, Flt-3L, IL-15, and IL-3, culturing them in a serum-free medium without an IL-3 containing IL-7, SCF, Flt-3L, and IL-15 to differentiate them into NK
progenitor cells, and culturing them in a serum-free medium containing IL-2, IL-7, SCF, Flt-3L, IL-15, and a serum substitute to differentiate them into mature NK cells.