PURPOSE: To obtain a new peptide having excellent persistence of a bronchodilating action by a smooth muscle relaxing action and useful for suppressing and improving of asthma, etc., as a bronchodilator.

CONSTITUTION: The objective peptide or its salt is expressed by the formula (A is Ala, Gly; B is Ile, Val; C is Asn, Ser; D is Thr, Ser; E is Leu, Tyr; F, I and J are each Lys, Arg, and at least one of these is Arg; G is Met, Leu or nLeu; K is Asn, Ala; L is Ser, Ala; M is Ile, Val; N is -NH2, Asn-NH2; excepting simultaneously A is Ala, B is Val, C is Asn, D is Thr, E is Leu, K is Asn, L is Ser, M is Ile and N is Asn-NH2). The peptide is obtained by, e.g. a solid phase synthesizing method wherein an amino acid is bonded to a C-end amino acid bonded to a benzhydrylamine resin, etc., one by one according to an amino acid sequence and removes the resin.