To provide a method for producing benzoxazine in a solvent-free system with extremely excellent mass-productivity.

Provided is a method for producing benzoxazine, which comprises heating a mixture of a primary amine, a phenol compound and formaldehyde, to synthesize benzoxazine by a condensation reaction through dehydration, characterized in that the primary amine, the phenol compound and formaldehyde are stirred by the vaporization of (i) water produced by the condensation reaction through dehydration occurring in heating the mixture of (a) the primary amine, (b) the phenol compound and (c) paraformaldehyde and/or an aqueous solution of formaldehyde and/or (ii) water contained in the aqueous solution of formaldehyde.