Disclosed are a process for preparation of an optically active 7-substituted 3-(2-aminopropyl)indole compound and an intermediate therefor. In the above preparation process, 7-substituted indole is reacted with L- or DL-serine in the presence of a tryptophan-synthesizing enzyme originating in microorganisms to form corresponding 7-substituted L-tryptophan, and it is subjected, if necessary, to reduction, protection, exchange and elimination.