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.