A method of producing an adhesive resin includes: a heating and kneading step of kneading a mixture containing a ring structure-containing hydrocarbon resin, an adhesive functional group-containing compound, and a peroxide while heating the mixture to obtain a heated and kneaded product; and a cooling and kneading step, performed in succession to the heating and kneading step, of kneading the heated and kneaded product while cooling the heated and kneaded product to obtain a cooled and kneaded product. The adhesive resin has a yellowness index (Yi) of 3.0 or less when 0.8 parts by mass of 2-(5-chloro-2-benzotriazolyl)-6-tert-butyl-p-cresol is added to 100 parts by mass of the adhesive resin.