To obtain the subject compound useful as an intermediate for medicines by a method high in the recovery of a resolving agent and in production efficiency by using an optically active acidic amino acid derivative as the resolving agent.

The mixture of a (+)-2-piperazinecarboxylic acid derivative with (-)-2-piperazinecarboxylic acid derivative as a raw material is brought into contact with a resolving agent such as an optically active N-acyl acidic amino derivative of the formula [R1 is H, a 1-10C alkyl; (n) is 1, 2] in an amount of 0.4-1.1 mole per mole of the raw material to produce the diastereoisomer salt. The obtained diastereoisomer salt is usually deposited from the solution at 0-100°C, and the deposited salt is disintegrated to separate the optically active (+)-2-piperazinecarboxylic acid derivative, etc., from the resolving agent.