This method for producing a crosslinked product of a carboxymethyl-group-containing modified hyaluronic acid and/or a salt thereof includes a step for obtaining the crosslinked product by irradiating a solution comprising a carboxymethyl-group-containing modified hyaluronic acid and/or a salt thereof with an electron beam.本發明為一種含有羧甲基之修飾玻尿酸及/或其鹽之交聯物之製造方法,其係包含對含有羧甲基之修飾玻尿酸及/或其鹽之溶液照射電子束,而得到交聯物之步驟。