Provided is a process for the preparation of t-butoxycarbonylamine compounds, which comprises using phosgene or a phosgene equivalent, t-butanol, and an organic base. Even when applied to a primary or secondary amine compound having low nucleophilicity, the process enables highly selective preparation of a t-butoxycarbonylamine compound at a low cost. In the process, a t-butoxycarbonylamine compound is prepared using: phosgene or a phosgene equivalent; t-butanol; an organic base; and either a primary or secondary amine compound or a primary or secondary ammonium salt.