An ECU performs atmospheric learning to correct an individual difference in an A/F sensor. In this case, when reducing fuel has been added before a fuel cut, the ECU calculates, at fixed intervals, the total amount of reducing fuel added and the total amount of oxygen flowing through an exhaust passage. The ECU then estimates the remaining amount of reducing fuel remaining in the exhaust passage using these total amounts, and performs atmospheric learning when the remaining amount is equal to or less than an allowable value. As a result, atmospheric learning can be accurately performed at the earliest possible timing even if the timing at which the reducing fuel is added or the operating state of an internal combustion engine or the like changes.