A substituted aryloxyurea of the formula: ##STR1## wherein Ar represents ##STR2## in which X.sup.7 represents a hydrogen atom, a halogen atom, a cyano group, a lower alkoxy group or a trifluoromethyl group, andR.sup.1 and R.sup.2 together form together with carbon and the nitrogen atom to which they are bonded a 4-8 membered heterocyclic ring.The substituted aryloxyureas exhibit an excellent herbicidal efficacy against weeds when applied, for example, to the weeds in a wide range of period from a preemergence stage to a growth stage.The substituted aryloxyureas of the invention have the excellent advantage of maintaining high safety on crops or crop plants in spite of their herbicidal efficacy.