Novel ethylamine derivatives represented by general formula (I) and pharmaceutically acceptable acid-addition salts thereof, wherein R1 represents hydrogen, hydroxy, lower alkoxy or halogeno; R2 represents C¿2-5? alkyl; R?3¿ represents hydrogen, C¿2-5? alkyl, C2-5 alkylcarbonyl, C6-10 aryl or C7-11 aralkyl; and the ring A means a bicyclic compound consisting of at least one benzene ring and a saturated or unsaturated 5- or 6-membered ring optionally containing heteroatom(s), provided that R?2 and R3¿ do not carry each two carbon atoms at the same time when the ring A is indole or 1,3-benzodioxole; and the ring A is a bicyclic compound other than indole or benzo[b]thiophene and R2 is a C¿3-5? alkyl when R?3¿ is hydrogen. Because of having catecholamine-potentiating effects and high selectivity for the CAE effect, these compounds are useful as psychotropic drugs, antidepressants, antiparkinson agents and antialzheimer agents.