An exhaust purification device of an internal combustion engine estimates a catalyst bed temperature from a detected value of the exhaust gas temperature (step S210), and calculates a switch amount of air that is used for determining whether or not the amount of addition of unburned fuel fraction needs to be corrected (step S220). Then, the device determines whether or not the actual amount of intake air detected is greater than the switch amount of air (step S240). If the actual amount of air exceeds the switch amount of air, it can be determined that the operation state of the engine is a state in which white smoke is likely to be produced, and therefore a correction of lessening the amount of addition of fuel provided from an fuel addition injector is performed (step S260).