Provide is a homogeneous sugar-chain added polypeptide, wherein the sugar-chain having interferon β activity. According to the present invention, a homogeneous sugar-chain added polypeptide having interferon β activity is produced by the method comprising the following steps: a step for synthesizing a sugar-chain added peptide fragment, and at least two peptide fragments, and a step for conjugating the sugar-chain added peptide fragment and at least two peptide fragments.本發明提供加成具有均一糖鏈構造之糖鏈之多胜肽中，加成具有干擾素β活性之糖鏈之多胜肽。依據本發明經由包含合成加成糖鏈之胜肽片段、至少2個胜肽片段之步驟，及連結加成糖鏈胜肽片段與至少2個胜肽片段之步驟之方法，即可製作具有均一糖鏈構造且具有干擾素β活性之加成糖鏈之多胜肽。
