A control device of an internal combustion engine to be applied to an internal combustion engine including: a fuel-mixing air supply means (31, 39, 41, 43) that supplies fuel-mixed air made of fuel including at least gasoline and air to a combustion chamber of the internal combustion engine; a catalyst arranged in an exhaust passage (34, 51, 52) through which an exhaust gas discharged from the combustion chamber passes; an air-fuel ratio sensor arranged in the exhaust passage on the downstream side of the catalyst, the air-fuel ratio sensor that generates an output value (Voxs) in accordance with the air-fuel ratio of the exhaust gas passing through the exhaust passage; and a target air-fuel ratio setting means that sets a target air-fuel ratio (abyfr) of the fuel-mixed air based on the output value from the air-fuel ratio sensor, the control device of the internal combustion engine comprising: a hydrogen concentration detection means (91, 82, 77) that detects hydrogen concentration (Ch) in the exhaust gas discharged from the combustion chamber; and a correction means that corrects the target air-fuel ratio set by the target air-fuel ratio setting means based on the hydrogen concentration detected by the hydrogen concentration detection means, characterized in that, the correction means sets the target air-fuel ratio (abyfr) to an air-fuel ratio on the rich side of the theoretical air-fuel ratio based on the output value (Voxs) of the air-fuel ratio sensor corresponding to a change in an interior of the catalyst from a reduction atmosphere that reduces the exhaust gas flowing into the catalyst to an oxidation atmosphere that oxidizes the exhaust gas flowing into the catalyst; the correction means sets the target air-fuel ratio to an air-fuel ratio on the lean side of the theoretical air-fuel ratio based on the output value of the air-fuel ratio sensor corresponding to a change in the interior of the catalyst from the oxidation atmosphere to the reduction atmosphere; and the air-fuel ratio sensor is a concentration cell type oxygen concentration sensor. a fuel-mixing air supply means (31, 39, 41, 43) that supplies fuel-mixed air made of fuel including at least gasoline and air to a combustion chamber of the internal combustion engine; a catalyst arranged in an exhaust passage (34, 51, 52) through which an exhaust gas discharged from the combustion chamber passes; an air-fuel ratio sensor arranged in the exhaust passage on the downstream side of the catalyst, the air-fuel ratio sensor that generates an output value (Voxs) in accordance with the air-fuel ratio of the exhaust gas passing through the exhaust passage; and a target air-fuel ratio setting means that sets a target air-fuel ratio (abyfr) of the fuel-mixed air based on the output value from the air-fuel ratio sensor, the control device of the internal combustion engine comprising: a hydrogen concentration detection means (91, 82, 77) that detects hydrogen concentration (Ch) in the exhaust gas discharged from the combustion chamber; and a correction means that corrects the target air-fuel ratio set by the target air-fuel ratio setting means based on the hydrogen concentration detected by the hydrogen concentration detection means, characterized in that, the correction means sets the target air-fuel ratio (abyfr) to an air-fuel ratio on the rich side of the theoretical air-fuel ratio based on the output value (Voxs) of the air-fuel ratio sensor corresponding to a change in an interior of the catalyst from a reduction atmosphere that reduces the exhaust gas flowing into the catalyst to an oxidation atmosphere that oxidizes the exhaust gas flowing into the catalyst; the correction means sets the target air-fuel ratio to an air-fuel ratio on the lean side of the theoretical air-fuel ratio based on the output value of the air-fuel ratio sensor corresponding to a change in the interior of the catalyst from the oxidation atmosphere to the reduction atmosphere; and the air-fuel ratio sensor is a concentration cell type oxygen concentration sensor. a hydrogen concentration detection means (91, 82, 77) that detects hydrogen concentration (Ch) in the exhaust gas discharged from the combustion chamber; and a correction means that corrects the target air-fuel ratio set by the target air-fuel ratio setting means based on the hydrogen concentration detected by the hydrogen concentration detection means, characterized in that, the correction means sets the target air-fuel ratio (abyfr) to an air-fuel ratio on the rich side of the theoretical air-fuel ratio based on the output value (Voxs) of the air-fuel ratio sensor corresponding to a change in an interior of the catalyst from a reduction atmosphere that reduces the exhaust gas flowing into the catalyst to an oxidation atmosphere that oxidizes the exhaust gas flowing into the catalyst; the correction means sets the target air-fuel ratio to an air-fuel ratio on the lean side of the theoretical air-fuel ratio based on the output value of the air-fuel ratio sensor corresponding to a change in the interior of the catalyst from the oxidation atmosphere to the reduction atmosphere; and the air-fuel ratio sensor is a concentration cell type oxygen concentration sensor.