To provide a method for preparing an optically active aminotetralin-1- one compound having a high optical purity by converting a specific optically active amino acid compound to an acid chloride, subjecting the obtained acid chloride to an acylation reaction, and further treating the acylated compound with a basic material.

An optically active amino acid compound of formula I [R1 and R2 are each H, OH, a 1-3C alkoxy or alkyl, or a halogen atom; R3 is H, an alkoxycarbonyl having a 1-4C alkoxy group, benzylcarbonyl or p- toluenesulfonyl; (S) is a configuration of S] is reacted with a halogenation agent in a solvent such as chlorobenzene to provide an acid chloride, and a Lewis acid such as titanium tetrachloride is allowed to act on the obtained acid chloride to carry out an acylation reaction. The Lewis acid is removed from the reaction liquid and the reaction liquid after removing the Lewis acid is treated with a basic material such as ammonia to provide the objective optically active aminotetralin-1-one compound of formula II [R1, R2 and (S) are each the same as the before] in the method for preparing the optically active aminotetralin-l-one.