In a multicylinder internal combustion engine including a turbocharger, the turbocharger employs a twin-entry turbo where a turbine includes two exhaust gas inflow ports. A first exhaust passage guides an exhaust gas discharged from a first cylinder group of the internal combustion engine to one exhaust gas inflow port of the turbocharger. A second exhaust passage guides an exhaust gas discharged from a second cylinder group of the internal combustion engine to the other exhaust gas inflow port of the turbocharger. An exhaust gas collecting portion of the first exhaust passage and an exhaust gas collecting portion of the second exhaust passage each include an air-fuel ratio sensor. This configuration allows efficiently contact of the exhaust gas on an element portion of the air-fuel ratio sensor, thus accurately detecting an air-fuel ratio of the exhaust gas at an upstream side of a catalyst for each cylinder.