For depolymerization of a cured epoxy resin material, used is a composition including a transition metal salt or a transition metal oxide containing a transition metal element (metal element that belongs to Groups 3-12 in the Periodic Table). In the reaction solvent, an oxidation occurs by the medium of the transition metal element so that the cured epoxy resin material may be depolymerized and decomposed. In this manner, it is possible to carry out depolymerization of a cured epoxy resin material at a temperature of 200° C., specifically 100° C. or lower very simply and rapidly, and to reduce the processing cost and energy requirement.