NOVELTY - A positive electrode active material comprises lithium transition metal oxide and an oxo-acid salt. Peak detected by transmission electron microscope-energy dispersive X-ray analysis of positive electrode active material cross-section includes peak (A) derived from element chosen from phosphorus, sulfur and boron, and peak (B) derived from transition metals. The ratio of intensity (I(A)50nm) of peak (A) in depth of 50 nm and intensity (I(A)5nm) of peak (A) in depth of 5 nm from the positive electrode active material surface is 0.00001-0.5.    USE - Positive electrode active material is used in positive electrode of nonaqueous electrolyte secondary battery (all claimed) used as power supply of consumer appliances and motor vehicle.    ADVANTAGE - The nonaqueous electrolyte secondary battery obtained using the positive electrode active material has excellent cycle characteristics, storage stability, and continuous charge characteristics.    DETAILED DESCRIPTION - A positive electrode active material comprises lithium transition metal oxide and oxo-acid salt. Peak detected by transmission electron microscope-energy dispersive X-ray analysis of positive electrode active material cross-section includes peak (A) derived from element chosen from phosphorus, sulfur and boron, and peak (B) derived from transition metals. The ratio of intensity (I(A)50nm) of peak (A) in depth of 50 nm from the positive electrode active material surface and intensity (I(A)5nm) of peak (A) in depth of 5 nm from the positive electrode active material surface is 0.00001-0.5. The intensity (I(B)50nm) of peak (B) in depth of 50 nm from positive electrode active material surface and intensity (I(B)5nm) of the peak (B) in depth of 5 nm from the positive electrode active material surface is 2-10000. INDEPENDENT CLAIMS are included for the following:    (1) positive electrode (120), which comprises positive electrode active material; and    (2) nonaqueous electrolyte secondary battery (100), which comprises positive electrode, negative electrode (130), nonaqueous electrolyte, and exterior component (160).    DESCRIPTION OF DRAWING(S) - The drawing shows a sectional view of nonaqueous electrolyte secondary battery.    Nonaqueous electrolyte secondary battery (100)    Separator (110)    Positive electrode (120)    Negative electrode (130)    Exterior component (160)