An internal combustion engine comprising: a supercharger configured to change a pressure of air fed into a combustion chamber, a variable valve timing mechanism (B, C) configured to change an amount of valve overlap between an intake valve and an exhaust valve, a catalyst which is arranged in an exhaust passage and which is configured to store oxygen, an upstream side air-fuel ratio sensor which is arranged at an upstream side of the catalyst and which is configured to detect an air-fuel ratio of inflowing exhaust gas flowing into the catalyst, a downstream side air-fuel ratio sensor which is arranged at a downstream side of the catalyst and which is configured to detect an air-fuel ratio of outflowing exhaust gas flowing out from the catalyst, and an air-fuel ratio control device controlling an air-fuel ratio of the inflowing exhaust gas, wherein, the air-fuel ratio control device is configured to set a target air-fuel ratio of the inflowing exhaust gas based on the air-fuel ratio detected by the downstream side air-fuel ratio sensor and to control the amount of fuel fed to the combustion chamber by feedback control so that the air-fuel ratio detected by the upstream side air-fuel ratio sensor matches the target air-fuel ratio when a blow-through amount of air blown from the intake passage through a cylinder to the exhaust passage due to an occurrence of valve overlap is a reference blow-through amount or less, and to set the target air-fuel ratio of the inflowing exhaust gas based on the air-fuel ratio detected by the downstream side air-fuel ratio sensor and, without performing feedback control using the upstream side air-fuel ratio sensor, to feed the amount of fuel calculated from the target air-fuel ratio to the combustion chamber when the blow-through amount is greater than the reference blow-through amount, characterized in that the air-fuel ratio control device is configured to switch the target air-fuel ratio of the inflowing exhaust gas based on the oxygen storage amount of the catalyst and the air-fuel ratio detected by the downstream side air-fuel ratio sensor, the oxygen storage amount of the catalyst being calculated based on the air-fuel ratio detected by the upstream side air-fuel ratio sensor when the blow-through amount is the reference blow-through amount or less and being calculated based on the target air-fuel ratio of the inflowing exhaust gas when the blow-through amount is greater than the reference blow-through amount. a supercharger configured to change a pressure of air fed into a combustion chamber, a variable valve timing mechanism (B, C) configured to change an amount of valve overlap between an intake valve and an exhaust valve, a catalyst which is arranged in an exhaust passage and which is configured to store oxygen, an upstream side air-fuel ratio sensor which is arranged at an upstream side of the catalyst and which is configured to detect an air-fuel ratio of inflowing exhaust gas flowing into the catalyst, a downstream side air-fuel ratio sensor which is arranged at a downstream side of the catalyst and which is configured to detect an air-fuel ratio of outflowing exhaust gas flowing out from the catalyst, and an air-fuel ratio control device controlling an air-fuel ratio of the inflowing exhaust gas, wherein, the air-fuel ratio control device is configured to set a target air-fuel ratio of the inflowing exhaust gas based on the air-fuel ratio detected by the downstream side air-fuel ratio sensor and to control the amount of fuel fed to the combustion chamber by feedback control so that the air-fuel ratio detected by the upstream side air-fuel ratio sensor matches the target air-fuel ratio when a blow-through amount of air blown from the intake passage through a cylinder to the exhaust passage due to an occurrence of valve overlap is a reference blow-through amount or less, and to set the target air-fuel ratio of the inflowing exhaust gas based on the air-fuel ratio detected by the downstream side air-fuel ratio sensor and, without performing feedback control using the upstream side air-fuel ratio sensor, to feed the amount of fuel calculated from the target air-fuel ratio to the combustion chamber when the blow-through amount is greater than the reference blow-through amount, characterized in that the air-fuel ratio control device is configured to switch the target air-fuel ratio of the inflowing exhaust gas based on the oxygen storage amount of the catalyst and the air-fuel ratio detected by the downstream side air-fuel ratio sensor, the oxygen storage amount of the catalyst being calculated based on the air-fuel ratio detected by the upstream side air-fuel ratio sensor when the blow-through amount is the reference blow-through amount or less and being calculated based on the target air-fuel ratio of the inflowing exhaust gas when the blow-through amount is greater than the reference blow-through amount.