PURPOSE: To make the promotion of improvement of fuel consumption and exhaust gas, by such means that, a multi-cylinder internal combustion engine be divided into two cylinder groups, with its one cylinder group made in use or not in use depending on the load, as well as with air inducted into the cylinder group when not in use.

CONSTITUTION: With multi-cyinders, not shown in the drawing, divided into a first and second group, each of them is linked to a first air suction pipe 3 and second air suction pipe 4. A first throttle valve 6 of the first air suction pipe 3 is made interlocking with a second throttle valve 8 of the second air suction pipe 4 through a lever 21, having a long groove 20, a big gear wheel 16 and a small gear wheel 23, with only the first throttle valve 6 opened at the time of low load and both of the valves 6, 8 opened at the time of high load. And in the downstream of the second throttle valve 8 of the second air suction pipe 4 is linked an atmospheric linking pipe 9, having an open- close valve 10, simultaneously with this valve 10 made interlocking with the throttle valve 8, and by a controller 31, applied a negative pressure from the first air suction pipe 3, the valve 10 is opened, when at the time of the second throttle valve 8 closing, to supply an air to the cylinder group not in use.