Novel 1-phenylakyl-3-phenylurea derivatives represented by the following formula (I): ##STR1## wherein R.sup.1 is an alkyl group of 1 to 8 carbon atoms, an alkoxy group of 1 to 5 carbon atoms or a halogen atom, R.sup.2 is an alkyl group of 1 to 15 carbon atoms, each of R.sup.3 and R.sup.4 is independently an alkyl group of 1 to 5 carbon atoms, m is an integer of 1 to 3, and n is 0 or 1, are provided. The compounds are potent in reducing the cholesterol level in serum, and useful for treating hyperlipemia and atherosclerosis.