An exhaust gas control system includes an upstream purification device (50, 50a, 50b) disposed in an exhaust passage (5, 5a, 5b, 5a', 5b') of the internal combustion engine (1), a downstream purification device (51, 51a, 51b) disposed in a portion of the exhaust passage downstream from the upstream purification device, a fuel addition valve (52, 52a, 52b) disposed in a portion of the exhaust passage upstream from the upstream purification device, and a urea addition valve (53, 53a, 53b) disposed in a portion of the exhaust passage between the upstream purification device and the downstream purification device, and a cooling device. The cooling device is configured such that refrigerant cools the fuel addition valve first and then cools the urea addition valve subsequent to the fuel addition valve.