A method for producing theanine including reacting a glutamic acid alkyl ester represented by general Formula (1): where R1 represents an alkyl group, with a ketone represented by general Formula (2): where R2 represents a hydrogen atom, R3 represents a lower alkanoyl group or a benzoyl group, and R2 and R3 may form a cycloalkanone ring in combination with the vicinal carbon atom, in the presence of t-butylamine, a secondary amine or a tertiary amine, reacting the resultant compound represented by general Formula (3): where R1, R2 and R3 are the same as defined above, with ethylamine, and then being subjected to heating in the presence of the ethylamine or reaction with a fatty acid.