The present invention provides a resonator including an upper case defining a portion of a resonance chamber and having a communicating hole communicating with the resonance chamber, a lower case integrally joined to the upper case and defining the resonance chamber together with the upper case, and an air pipe which is blow molded with the upper case being inserted, which is joined to an outer surface of the upper case where the communicating hole opens, an inside of which forms a gas passage, and which is defined with a through hole forming a common hole with the communicating hole, wherein the air pipe is blow molded by using polypropylene resin and the lower case is molded by using a nylon resin. In the resonator of the invention, because the resonator itself has heat resistance, it is unnecessary to dispose a heat insulator or the like, thereby decreasing the number of parts and the cost.