Disclosed is an azapeptide derivative represented by the formula (I): ##STR1## wherein A represents a direct bond, an .alpha.-amino acid or a residue of a dipeptide; R.sup.1 represents a hydrogen atom or a protective group for a terminal amino group; R.sup.2 represents a phenyl group or a phenyl group substituted by one or two substituents selected from the group consisting of a lower alkyl group, halogen atom, hydroxyl group which may be protected, nitro group, amino group which may be protected and perhalo lower alkyl group; and R.sup.3 represents a hydroxyl group or a protective group for a terminal carboxyl group, and a salt thereof, and an agent for curing nervous inflammation of respiratory apparatus, asthma and bronchospasm comprising the azapeptide derivative represented by the formula (I) or a salt thereof as an active ingredient.