This inorganic material separation method includes the following steps which are performed in the given order: a contact step in which a composite material is brought into contact with a processing liquid, said composite material including a first organic substance which is decomposed by the processing liquid, a second organic substance which is not decomposed by the processing liquid, and an inorganic material; a separation step in which the processing liquid including decomposition products of the first organic substance, and a recovered substance including the inorganic material and the second organic substance are separated; and a heat treatment step in which the recovered substance is heat treated at a temperature equal to or higher than a temperature at which the second organic substance is eliminated.