The present invention relates to a method for decomposing, in the presence of subcritical water, a thermosetting resin comprising a polyester moiety and a crosslinking moiety therewith to provide a compound comprising an acid residue derived from the polyester moiety and a residue derived from the crosslinking moiety, and collecting the compound in an efficient yield, specifically, which comprises steps of: (I) decomposing the thermosetting resin in the presence of subcritical water to provide a solid comprising a compound comprising an acid residue derived from the polyester moiety and a residue derived from the crosslinking moiety, (II) subjecting the solid to an organic solvent to dissolve the compound into the organic solvent, wherein the organic solvent has a higher solubility which can dissolve the compound than that of water, and (III) collecting, separating or isolating the compound from the organic solvent.