A cured epoxy resin material is depolymerized by using a composition including a compound represented by the chemical formula of XOmYn (wherein X is hydrogen, alkali metal or alkaline earth metal, Y is halogen, m is a number satisfying 1≦m≦8 and n is a number satisfying 1≦n≦6), and a reaction solvent, wherein X is capable of being dissociated from XOmYn and Y radical is capable of being produced from XOmYn in the reaction solvent. It is possible to carry out depolymerization of a cured epoxy resin material, for example, at 200° C., specifically 100° C. or lower, and to reduce a processing cost and an energy requirement. It is also possible to substitute for a reaction system using an organic solvent as main solvent, so that the contamination problems caused by the organic solvent functioning as separate contamination source may be solved and environmental contamination or pollution may be minimized.