An exhaust gas control system of an internal combustion engine includes a urea water tank, a heater, a purifying device, a notification device, and a controller. The controller is configured to determine whether frozen urea water is left or not. The controller is configured to determine whether liquid urea water capable of being pumped out is not left or not. The controller is configured to estimate a suppliable amount of the urea water to the urea water tank in response to a state where the frozen urea water is left, and the controller configured to control the notification device so as to give a notification for prompting a supply of the suppliable amount of the urea water to the urea water tank in response to a state where liquid urea water capable of being pumped out is not left.