Abstract: A method of producing a cathode active material for a secondary battery is provided. The method includes preparing a mixture comprising a lithium source, a phosphate source, an iron source, a carbon source, a boron source comprising an oxo acid of boron, and a liquid medium; granulating the mixture to obtain a precursor; and heat-treating the precursor to obtain a lithium transition metal compound having an olivine structure, wherein in the mixture, a total molar amount of boron atoms contained in the boron source is more than 0% and less than 3% with respect to a total molar amount of iron atoms contained in the iron source as 100%.