An exhaust gas control apparatus for an internal combustion engine comprising: a selective reduction catalyst that is disposed in an exhaust passage of an internal combustion engine , and reduces a nitrogen oxide in exhaust gas with ammonia as a reducing agent; a urea solution supply device that is installed at an upstream side of the selective reduction catalyst , and supplies a urea solution to the exhaust passage ; and a control device configured to control the urea solution supply device so that a urea solution in a target supply amount corresponding to a concentration of a nitrogen oxide flowing into the selective reduction catalyst is supplied to the selective reduction catalyst , wherein the control device is further configured to control the urea solution supply device so that a urea solution in a supply amount at an abnormality diagnosis time that is a larger supply amount than the target supply amount is supplied to the selective reduction catalyst , diagnose presence or absence of abnormality of the selective reduction catalyst in accordance with an amount of ammonia that is discharged to a downstream side of the selective reduction catalyst , while the urea solution in the supply amount at the abnormality diagnosis time is supplied, and control the urea solution supply device so that a supply amount of the urea solution becomes smaller than the target supply amount when an estimated amount of ammonia adsorbed by the selective reduction catalyst is larger than a reference adsorption amount, and an amount of a urea solution that is required in removal of nitrogen oxide per unit is smaller than a reference urea solution amount, after diagnosis of presence or absence of abnormality of the selective reduction catalyst . a selective reduction catalyst that is disposed in an exhaust passage of an internal combustion engine , and reduces a nitrogen oxide in exhaust gas with ammonia as a reducing agent; a urea solution supply device that is installed at an upstream side of the selective reduction catalyst , and supplies a urea solution to the exhaust passage ; and a control device configured to control the urea solution supply device so that a urea solution in a target supply amount corresponding to a concentration of a nitrogen oxide flowing into the selective reduction catalyst is supplied to the selective reduction catalyst , wherein the control device is further configured to control the urea solution supply device so that a urea solution in a supply amount at an abnormality diagnosis time that is a larger supply amount than the target supply amount is supplied to the selective reduction catalyst , diagnose presence or absence of abnormality of the selective reduction catalyst in accordance with an amount of ammonia that is discharged to a downstream side of the selective reduction catalyst , while the urea solution in the supply amount at the abnormality diagnosis time is supplied, and control the urea solution supply device so that a supply amount of the urea solution becomes smaller than the target supply amount when an estimated amount of ammonia adsorbed by the selective reduction catalyst is larger than a reference adsorption amount, and an amount of a urea solution that is required in removal of nitrogen oxide per unit is smaller than a reference urea solution amount, after diagnosis of presence or absence of abnormality of the selective reduction catalyst . <EOS>