A method of manufacturing an active material having a sufficient discharge capacity at a high discharge current density, an active material obtained thereby, an electrode using the same, and a lithium-ion secondary battery equipped therewith are provided. The method of manufacturing an active material comprises a step of polymerizing a mixture containing an Fe ion, an Li ion, a PO4 ion, a hydroxy acid, and a polyol, the mixture containing the polyol by a molar ratio 1.3 to 16 times that of the hydroxy acid, so as to yield a polymer; and a step of heating the polymer, so as to yield an active material containing an active material particle and carbon. The active material particle is mainly composed of LiFePO4.