<;P>;PROBLEM TO BE SOLVED: To provide an excellent NK activity enhancer that by specifying a strain belonging to Lactobacillus plantarum, surely exhibiting activity action on human NK cells. <;P>;SOLUTION: The NK activity enhancer includes a cell body of viable microbe and/or dead microbe of Lactobacillus plantarum HSK201 strain (NITEP-589), a culture product of cell body, a treated product of cell body or an extract thereof as an active ingredient. <;P>;COPYRIGHT: (C)2010,JPO&INPIT