A method of treating a composite material of epoxy resin-cured product and inorganic matter to easily recover the resin components in a recyclable state without causing thermal decomposition. A method of separating the inorganic matter. The epoxy resin-cured product is treated with a treatment liquid which contains a decomposition catalyst for epoxy resin-cured products and an organic solvent to decompose and dissolve the epoxy resin-cured product. A composite material of epoxy resin-cured product and inorganic matter is also treated to decompose and dissolve the epoxy resin-cured product in the above-mentioned manner and the inorganic matter is then separated from the liquid.