PURPOSE: To get a resonance intake effect in all speed ranges of a prime mover by installing in the point midway in an intake pipe.

CONSTITUTION: Intake air passes through a throttle body 1 and then passes the inner part of a manifold from the inside of a chamber 2. This manifold reenters the chamber 2, but it gets in so as to pierce through this chamber 2 in which a taper piece 5 for separating the manifold serves as a part of this manifold, thus it is connected to another manifold at the side of a prime mover. A flow of intake air at low speed passes through the chamber 2 from the throttle body 1, passing the manifold as describing a circle and piercing through the chamber 2, and then it is conducted into a cylinder of the prime mover. When it goes to high speed, the taper piece 5 in the chamber 2 is separated from the manifold at the prime mover side, whereby the intake air run past the throttle body 1 gets into the manifold at the prime mover side directly from the chamber.