A control device of an internal combustion engine includes a target air-fuel ratio set portion that sets a target air-fuel ratio according to an operating state of the internal combustion engine, an air-fuel ratio detection portion that detects an actual air-fuel ratio, a feedback correction value calculation portion that calculates a feedback correction value to correct a fuel injection amount for the actual air-fuel ratio to coincide with the target air-fuel ratio, and a fuel property change determination portion that determines a change of a fuel property on the basis of a change of a correction amount including a correction value for the fuel injection amount calculated on the basis of the feedback correction value in addition to the feedback correction value. The control device can determine a change of the fuel property accurately even when a change of the feedback correction value is reflected on another correction value.