To prevent the occurrence of such an exhaust cycle as being subject to a minus effect with one another, of individual cylinders put together in a group in order to attain a high torque level on the whole.

This exhaust system for a multicylinder internal combustion engine provided with each individual piece of exhaust lines 4, 6, 12; 5, 7, 13 and two groups 2 and 3 of cylinders, is equipped with a connecting pipe 16 lying between the exhaust lines set up in a spot nearby the engine. The connecting pipe 16 is made up as a resonant pipe, whereby it is formed into being interruptible or cutoff releasable in depending on at least one operational parameter of the internal combustion engine. Owing to the connecting pipe 16 working as the resonant pipe, resonance between both these exhaust lines is generated in dependence on the firing order and rotational frequency of the internal combustion engine. When a resonance action worsens a torque variation depending on the rotational frequency, a cutoff valve 17 is closed, and when the resonance action is favorably working on the torque variation, the cutoff valve 17 is opened to operate.