Phenethylamine derivatives shown by the general formula ##STR1## wherein Ro represents a lower alkyl group; R.sub.1 represents a lower alkyl group or a lower alkoxy group; R.sub.2 represents hydrogen atom or a hydroxyl group; R.sub.3 and R.sub.4 each represents hydrogen atom or a lower alkyl group; R.sub.5 represents hydrogen atom or a lower alkoxy group; X represents oxygen atom or a methylene group; m is an integer of 1-3; and n is an integer of 0-2 and the acid addition salts thereof.These compounds exhibit a strong .alpha.-adrenergic blocking action and are useful as an antihypertensive agent.