An internal combustion engine control device that controls an internal combustion engine using a calculated air-fuel ratio correction amount, the internal combustion engine including a catalyst disposed in an exhaust pipe, a first exhaust gas sensor disposed on an upstream side of the catalyst , and a second exhaust gas sensor disposed on a downstream side of the catalyst , the internal combustion engine control device comprising: An oxygen storage ratio calculation unit that calculates an oxygen storage ratio of the catalyst based on a catalytic reaction model having at least a detection value of the first exhaust gas sensor as an input; a statistical model calculation unit that predicts a catalyst downstream exhaust gas concentration by using a statistical model having the oxygen storage ratio as an input and the catalyst downstream exhaust gas concentration as an output; and an air-fuel ratio correction amount calculation unit that calculates an air-fuel ratio correction amount of an air-fuel mixture of the internal combustion engine based on a future catalyst downstream exhaust gas concentration calculated by the statistical model calculation unit , characterized in that the catalytic reaction model is defined by a reaction rate between at least oxygen on the upstream side of the catalyst , carbon monoxide on the upstream side of the catalyst , and a metal carried in the catalyst, wherein the oxygen storage ratio calculation unit includes: an oxygen concentration calculation unit that calculates an oxygen concentration on the upstream side of the catalyst (21() based on a detection value of a first exhaust gas sensor on the upstream side of the catalyst ; and a carbon monoxide concentration calculation unit that calculates a carbon monoxide concentration on the upstream side of the catalyst based on the detection value of the first exhaust gas sensor on the upstream side of the catalyst . An oxygen storage ratio calculation unit that calculates an oxygen storage ratio of the catalyst based on a catalytic reaction model having at least a detection value of the first exhaust gas sensor as an input; a statistical model calculation unit that predicts a catalyst downstream exhaust gas concentration by using a statistical model having the oxygen storage ratio as an input and the catalyst downstream exhaust gas concentration as an output; and an air-fuel ratio correction amount calculation unit that calculates an air-fuel ratio correction amount of an air-fuel mixture of the internal combustion engine based on a future catalyst downstream exhaust gas concentration calculated by the statistical model calculation unit , characterized in that the catalytic reaction model is defined by a reaction rate between at least oxygen on the upstream side of the catalyst , carbon monoxide on the upstream side of the catalyst , and a metal carried in the catalyst, wherein the oxygen storage ratio calculation unit includes: an oxygen concentration calculation unit that calculates an oxygen concentration on the upstream side of the catalyst (21() based on a detection value of a first exhaust gas sensor on the upstream side of the catalyst ; and a carbon monoxide concentration calculation unit that calculates a carbon monoxide concentration on the upstream side of the catalyst based on the detection value of the first exhaust gas sensor on the upstream side of the catalyst . an oxygen concentration calculation unit that calculates an oxygen concentration on the upstream side of the catalyst (21() based on a detection value of a first exhaust gas sensor on the upstream side of the catalyst ; and a carbon monoxide concentration calculation unit that calculates a carbon monoxide concentration on the upstream side of the catalyst based on the detection value of the first exhaust gas sensor on the upstream side of the catalyst . <EOS>