An exhaust gas control apparatus for an internal combustion engine, the internal combustion engine including a combustion chamber and an exhaust passage, the exhaust gas control apparatus comprising: a urea adding valve configured to add urea water to exhaust gas discharged from the combustion chamber to the exhaust passage; selective reduction-type catalyst devices (41, 42) configured to reduce nitrogen oxide in the exhaust gas by selective catalytic reduction in which ammonia generated from the urea water is used as a reducing agent; an ammonia slip catalyst device in which an oxidation catalyst is supported, the ammonia slip catalyst device being placed on a downstream side of the selective reduction-type catalyst devices (41, 42), and the ammonia slip catalyst device being configured to oxidize the ammonia flowing out from the selective reduction-type catalyst devices (41, 42); a fuel addition device (30; 18) configured to add an unburned fuel to burned gas burned in the combustion chamber; characterised by an electronic control unit comprising means to control the fuel addition device (30; 18) as an amount-increasing processing when the amount of the nitrogen oxide flowing out from the selective reduction-type catalyst devices (41, 42) is not reduced to a desired amount with respect to the amount of the nitrogen oxide flowing into the selective reduction-type catalyst devices (41, 42) and when a catalyst bed temperature of the ammonia slip catalyst device is within a temperature region where the nitrogen oxide in the exhaust gas can be reduced in the ammonia slip catalyst device by selective catalytic reduction in which unburned hydrocarbon added to the exhaust by the fuel addition device (30; 18) is used as a reducing agent, wherein the amount of the hydrocarbon in the exhaust gas flowing into the ammonia slip catalyst device is increased based on the current catalyst bed temperature of the ammonia slip catalyst device and the amount of nitrogen oxide flowing into the ammonia slip catalyst device. a urea adding valve configured to add urea water to exhaust gas discharged from the combustion chamber to the exhaust passage; selective reduction-type catalyst devices (41, 42) configured to reduce nitrogen oxide in the exhaust gas by selective catalytic reduction in which ammonia generated from the urea water is used as a reducing agent; an ammonia slip catalyst device in which an oxidation catalyst is supported, the ammonia slip catalyst device being placed on a downstream side of the selective reduction-type catalyst devices (41, 42), and the ammonia slip catalyst device being configured to oxidize the ammonia flowing out from the selective reduction-type catalyst devices (41, 42); a fuel addition device (30; 18) configured to add an unburned fuel to burned gas burned in the combustion chamber; characterised by an electronic control unit comprising means to control the fuel addition device (30; 18) as an amount-increasing processing when the amount of the nitrogen oxide flowing out from the selective reduction-type catalyst devices (41, 42) is not reduced to a desired amount with respect to the amount of the nitrogen oxide flowing into the selective reduction-type catalyst devices (41, 42) and when a catalyst bed temperature of the ammonia slip catalyst device is within a temperature region where the nitrogen oxide in the exhaust gas can be reduced in the ammonia slip catalyst device by selective catalytic reduction in which unburned hydrocarbon added to the exhaust by the fuel addition device (30; 18) is used as a reducing agent, wherein the amount of the hydrocarbon in the exhaust gas flowing into the ammonia slip catalyst device is increased based on the current catalyst bed temperature of the ammonia slip catalyst device and the amount of nitrogen oxide flowing into the ammonia slip catalyst device.