A positive electrode active material for a nonaqueous electrolyte secondary battery that is constituted by a lithium nickel composite oxide that combines a high capacity with excellent thermal stability, a manufacturing method suitable for industrial production, and a nonaqueous electrolyte secondary battery of high safety. A positive electrode active material for a nonaqueous electrolyte secondary battery includes a lithium nickel composite oxide represented by the following composition formula (1): LibNi1-aM1aO2  (1) (where M1 represents at least one element selected from transition metal elements other than Ni, elements of the second group of the Periodic System and elements of the thirteenth group of the Periodic System; a satisfies the condition 0.01≤a≤0.5; and b satisfies the condition 0.85≤b≤1.05). The content of carbon in the lithium nickel composite oxide is equal to or less than 0.08% by mass.