非常感謝您的答復。我之前看到移民局的信息（見内）也感到沒問題，但是他單位的移民律師認爲要同居至入籍才行

However, the statute does not require living in marital union for the period between the date of filing the application and the date of naturalization (date applicant takes the Oath of Allegiance). The corresponding regulation conflicts with the statute in stating that the spouse must have been living in marital union with his or her citizen spouse for at least 3 years at the time of the examination on the application, and not at the time of filing.

USCIS follows the language of the statute in requiring living in marital union only up until the time of filing.[5] Accordingly, only the existence of a legally valid marriage is required from the date of filing the application until the time of the applicant’s naturalization.[6]