An exhaust gas control device of an internal combustion engine has an exhaust treatment device that purifies an exhaust gas. The exhaust gas control device is formed such that unburned fuel is supplied into the exhaust gas by a fuel addition valve, and the unburned fuel is ignited by a glow plug, to generate thereby a flame that reaches an upstream end of an exhaust treatment device. The unburned fuel is caused to become adhered to the upstream end of the exhaust treatment device before a generated flame reaches the exhaust treatment device. Then, the unburned fuel adhered to the upstream end of the exhaust treatment device burns by the flame.