Positive active material for lithium secondary battery comprising a particle size distribution

Disclosed is a cathode active material for lithium secondary batteries containing lithium transition metal composite oxide in the form of primary particles having a one-body structure, the cathode active material having a ratio (R/L) of a right area (R) to a left area (L) in a particle size distribution (PSD) graph of less than 1.1, based on a maximum point of a main peak in the particle size distribution (PSD) graph, in which an X-axis represents a particle size (μm) and a Y-axis represents a relative particle amount (%).