An object of the present invention is to realize more effective intercalation and deintercalation of lithium ions in a cathode active material. The preset invention provides a cathode active material plate-like particle for a lithium secondary battery, the particle having a layered rock salt structure, wherein lithium-intercalation/deintercalation-plane-oriented grains (primary crystal grains whose (003) plane is oriented so as to intersect a plate surface of the plate-like particle) are present in a dispersed state among numerous (003)-plane-oriented grains (primary crystal grains whose (003) plane is oriented in parallel with the plate surface of the plate-like particle).