An exhaust gas control apparatus for an internal combustion engine includes a urea water injection valve, a catalyst disposed in an exhaust passage downstream of the injection valve, and an electronic control unit. The injection valve is configured to add urea water to exhaust gas. The catalyst is configured to adsorb ammonia generated from the urea water. The electronic control unit is configured to (i) set a target adsorption amount of the ammonia adsorbed on the catalyst, (ii) control the injection valve such that the amount of the urea water added to the exhaust gas becomes an addition amount calculated based on the target adsorption amount, and (iii) execute an initialization processing for decreasing the amount of the ammonia adsorbed on the catalyst to (zero) when an integrated value of the amount of the NOx flowing into the catalyst is equal to or higher than a predetermined value.