To realize a method for producing a compound useful as a resolving agent for other racemic compounds in relative good vessel efficiency by optically resolving (RS)-1-phenylethylamine in the presence of a specific inexpensive resolving agent.

This method for producing the optically active 1- phenylethylamine comprises heating (RS)-1-phenylethylamine and optically active lactic acid in a solvent at approximately 50°C with stirring, cooling the obtained homogeneous solution or distilling off the solvent from the solution to deposit the crystals of a slightly soluble salt among the diastereoisomer salts formed from the optically active 1-phenylethylamine and the optically active lactic acid, filtering off the crystal, concentrating the left filtrate to obtain the other diastereoisosmer salt, and subsequently decomposing the separated diastereoisomer salts, respectively. The optically active lactic acid is suitably used in an amount of 0.5-1.5 moles per mole of the (RS)-1-phenylethylamine.