A method of producing a material capable of electrochemically storing and releasing a large amount of lithium ions is provided. The material is used as an electrode material for a negative electrode, and includes silicon or tin primary particles composed of crystal particles each having a specific diameter and an amorphous surface layer formed of at least a metal oxide, having a specific thickness. Gibbs free energy when the metal oxide is produced by oxidation of a metal is smaller than Gibbs free energy when silicon or tin is oxidized, and the metal oxide has higher thermodynamic stability than silicon oxide or tin oxide. The method of producing the electrode material includes reacting silicon or tin with a metal oxide, reacting a silicon oxide or a tin oxide with a metal, or reacting a silicon compound or a tin compound with a metal compound to react with each other.