An optically active 3-aminopyrrolidine (3AP) salt has a high optical purity which is useful as an intermediate in an industrial production method of an optically active 3AP, an efficient method for producing it, and an efficient industrial method for optical resolution of 3AP. Optical resolution of 3AP is efficiently carried out by reacting racemic 3AP with optically active 2-methoxyphenylacetic acid in the presence of a mineral acid such as hydrochloric acid in an aqueous solvent, followed by separation of the resulting diastereomer salt constituted by 1 mole of optically active 3AP and 2 moles of optically active 2-methoxyphenylacetic acid.