To provide ducts with a resonator which secure air tightness even under vibration and the like and can be low costwise.

In the both sides of a resonator 3 in a hollow box shape, tubular bodies 42, 52 are built orienting toward a void space S formed by the resonator 3. Slits 43, 53 are formed on the tubular bodies 42, 52, and small protrusions 15, 25 are provided at the distal ends of circumferential faces of two ducts 1, 2. By fitting the small protrusions 15, 25 into the slits 43, 53 both ducts 1, 2 can be inserted into the tubular bodies 42, 52 of the resonator 3.