An (R)-2-amino-1-phenylethanol derivative shown by the general formula (IIa) wherein R1 and R5 represent a hydrogen atom, etc.; R2, R3 and R4 independently represent a halogen atom, etc., or a salt thereof, can readily be produced (1) by permitting a microorganism belonging to the genus Rhodosporidium, the genus Comamonas or the like to act on a mixture of corresponding (R)-form and (S)-form to asymmetrically utilize, or (2) by permitting a microorganism belonging to the genus Lodderomyces, the genus Pilimelia or the like to act on a corresponding aminoketone derivative to asymmetrically reduce. An (R,R)-1-phenyl-2-[(2-phenyl-1-alkylethyl)amino]ethanol derivative having a high optical purity can easily be obtained from the compound of the formula (IIa) or a salt thereof. Said derivative is useful as an intermediate for producing an anti-obesity agent and so on.