An internal combustion engine is provided with a hydrocarbon feed valve arranged in an engine exhaust passage. When injection control for injecting hydrocarbons from the hydrocarbon feed valve for exhaust treatment is stopped, to prevent the hydrocarbon feed valve from clogging, hydrocarbons for preventing clogging are injected from the hydrocarbon feed valve when the engine is not discharging soot, that is, when the feed of fuel to the inside of the combustion chamber is stopped and, after hydrocarbons for preventing clogging are injected once, the injection of hydrocarbons for preventing clogging from the hydrocarbon feed valve is stopped until injection control for exhaust treatment is started.