An exhaust introduction path is bifurcated on the exit side of a valve into paths whose number is equal to the number of exhaust openings of an internal combustion engine, and the portion of the bifurcation is located at a position directly facing a movable valve body of the valve. This causes the exhaust gas to flow easily only in the direction of the exit. By this, each exhaust gas introduction path communicating with a suction opening is shut off as much as possible from the other introduction paths so that they are substantially not communicated to each other.
