Cathode active material, cathode, and nonaqueous electrolyte secondary battery

The present invention provides a nonaqueous electrolyte secondary battery which includes a cathode having a cathode active material layer, an anode, and a nonaqueous electrolyte, wherein the cathode active material layer includes secondary particles of a lithium phosphate compound having olivine structure, an average particle diameter A of primary particles constituting the secondary particles is 50 nm or more and 500 nm or less, and a ratio B/A of a pore diameter B of the secondary particles to the average particle diameter A of the primary particles is 0.10 or more and 0.90 or less.