A positive electrode active material for a lithium ion secondary battery is lithium vanadium phosphate represented by a following composition expression (1) and in which a peak intensity ((002)int/(201)int) of a (002) plane normalized with respect to a peak intensity of a (201) plane and a peak intensity ((102)int/(201)int) of a (102) plane normalized with respect to a peak intensity of the (201) plane in an X-ray diffraction pattern satisfy 0.35≤(002)int/(201)int≤0.53 and 0.46≤(102)int/(201)int≤0.63, respectively, LixVOPO4 . . . (1).