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.