The air-fuel ratio feedback control section updates an air-fuel ratio feedback correction value. The air-fuel ratio learning control section performs, in each of learning regions, learning of an air-fuel ratio learning value. If the air-fuel ratio feedback correction value converges to a value less than or equal to a specified value, the air-fuel ratio learning control section determines that learning of the air-fuel ratio learning value in the learning region has been completed. If it has not yet been determined that learning of the air-fuel ratio learning value has been completed in any of the learning regions, the air-fuel ratio learning control section collectively updates the air-fuel ratio learning values of all the learning regions at the time of updating the air-fuel ratio learning value through learning in any of the learning regions.