PURPOSE: To effectively prevent the erroneous operation of a control valve due to the shortage of the intake negative pressure by installing a plurality of control valves for varying the characteristic frequency of an intake system to plural stages according to the operation state and setting the operation characteristic so that the intake negative pressure does not act at the same time to the negative pressure actuator of each control valve.

CONSTITUTION: An intake passage 11 is equipped with independent intake passages 15,... whose downstream edges are connected with a combustion chamber 10 and the left and right collection intake passages 16L and 16R in pair where the upstream edges of the independent intake passages 15 for the respective banks 1L and 1R are collected and connected. The collection intake passages 16L and 16R are allowed to communicate through the first communication passage 20 for connecting the downstream side edge parts and the second communication passage 21 for connecting the intermediate parts, and the first control valve 22 in always open state is arranged in the first communication passage 20, and the second control valve 23 which is in always closed state is arranged in the second communication passage 21. The introduction of the intake negative pressure into the negative pressure actuators 24 and 25 is controlled according to the engine revolution speed, and the resonance harmonized revolution speed is varied between both the collection intake passages 16L and 16R by opening/closing-selecting both control valves 22 and 23, and the output torque of the engine 1 is increased by the resonance supercharge.