A cinnamoylamide derivative of general formula: ##STR1## [wherein, (i) in case that R.sup.2 represents a methyl group and R.sup.3 represents a hydrogen atom,(R.sup.1).sub.n represents a group selected out of3-pentyl group,4-pentyl group,4-neopentyl group,4-(2-ethylbutyl) group,4-(2-methylpentyl) group,2-fluoro-4-pentyloxy group,4-butylthio group,4-cyclobutylmethyl group,4-cyclohexylmethyl group,4-(4-phenylbutyl) group and4-phenoxy group, and(ii) in case that R.sup.2 represents a hydrogen atom and R.sup.3 represents a methyl group,(R.sup.1).sub.n represents a group selected out of3-pentyl group and4-phenethyl group.]or non-toxic salts thereof possess an inhibitory activity on 5.alpha.-reductase, and therefore be useful for treating and/or preventing agent for alopecia, acnes or prostatic hypertrophy.