A naphthalene derivative having the formula is new and useful for medicine. ##STR1## wherein R.sup.1 represents a hydrogen atom, a lower alkyl group or an acyl group;R.sup.2 independently represents a hydrogen atom, a lower alkyl group, a lower alkoxy group, a halogen atom, a cycloalkyl group, a cycloalkylalkyl group, a hydroxyl group, an aryl group which may be substituted, an arylalkyl group whose aryl group may be substituted, a heteroaryl group, or a heteroarylalkyl group;R.sup.3 and R.sup.4 are the same or different and represent a hydrogen atom, a lower alkyl group, a lower alkenyl group, an aryl group which may have a substituent, an arylalkyl group whose aryl group may be substituted, an arylalkenyl group whose aryl group may be substituted, a cycloalkyl group, an alkoxyalkyl group, a heteroaryl group, a heteroarylalkyl group, a carboxyl group, a carboxyalkyl group, an aminoalkyl group, or a cyano group;R.sup.5 represents a group of the formula, --OR.sup.7, (wherein R.sup.7 represents a hydrogen atom or a lower alkyl group), or a group of the formula, ##STR2## (wherein R.sup.8 and R.sup.9 are the same or different and represent a hydrogen atom or a lower alkyl group.