A surface treatment method of a metal material, comprising: attaching an electron releasing-related substance onto a surface of the metal material in an adsorption process; and applying a chemical conversion treatment to the metal material having the electron releasing-related substance attached thereto, using a chemical conversion treatment agent, in a chemical conversion process which is provided before an electrodeposition coating process such that an energy band gap of a finally-formed chemical conversion film is smaller than that of a chemical conversion film formed by using only the chemical conversion treatment agent, wherein an electron releasing substance to make the energy band gap of the finally-formed chemical conversion film be smaller than that of the chemical conversion film formed by using only the chemical conversion treatment agent is used as said electron releasing-related substance so that said finally-formed chemical conversion film can be the chemical conversion film formed by using only the chemical conversion treatment agent which contains said electron releasing substance, wherein at least one kind of metal fine particles, n-type semiconductor fine particles, preferably n-type ZnO, intrinsic semiconductor fine particles, electrically conductive organic fine particles, and electrical insulator fine particles is used as said electron releasing substance, wherein the electrical insulator fine particle is an oxide compound selected from ZnO and TiO 2, and wherein a compound having at least one selected from a group consisting of Zr, Ti, Hf and Si as a primary component is used as said chemical conversion treatment agent so that the chemical conversion film is formed by an oxide compound having at least one selected from the group consisting of Zr, Ti, Hf and Si. attaching an electron releasing-related substance onto a surface of the metal material in an adsorption process; and applying a chemical conversion treatment to the metal material having the electron releasing-related substance attached thereto, using a chemical conversion treatment agent, in a chemical conversion process which is provided before an electrodeposition coating process such that an energy band gap of a finally-formed chemical conversion film is smaller than that of a chemical conversion film formed by using only the chemical conversion treatment agent, wherein an electron releasing substance to make the energy band gap of the finally-formed chemical conversion film be smaller than that of the chemical conversion film formed by using only the chemical conversion treatment agent is used as said electron releasing-related substance so that said finally-formed chemical conversion film can be the chemical conversion film formed by using only the chemical conversion treatment agent which contains said electron releasing substance, wherein at least one kind of metal fine particles, n-type semiconductor fine particles, preferably n-type ZnO, intrinsic semiconductor fine particles, electrically conductive organic fine particles, and electrical insulator fine particles is used as said electron releasing substance, wherein the electrical insulator fine particle is an oxide compound selected from ZnO and TiO 2, and wherein a compound having at least one selected from a group consisting of Zr, Ti, Hf and Si as a primary component is used as said chemical conversion treatment agent so that the chemical conversion film is formed by an oxide compound having at least one selected from the group consisting of Zr, Ti, Hf and Si.