A method for separating metal components from a treatment material containing a silicate and metal elements includes: a reaction step of reacting the treatment material and a molten alkali hydroxide in which bubbles due to water vapor derived from water are generated by heating a hydroxide of an alkali metal or an alkaline-earth metal and the water in a state where the hydroxide and the water coexist, to obtain a reaction product; and a first precipitation step of dissolving the reaction product of the treatment material and the molten alkali hydroxide after the reaction step in water, thereby generating a precipitate containing the metal elements.