An air-fuel ratio feedback control range is enlarged to improve exhaust
purification performance and output stability. In one aspect, an air-fuel
ratio control apparatus of an internal combustion engine comprises an
air-fuel ratio sensor capable of detecting an air-fuel ratio across both
lean and rich ranges with a theoretical air-fuel ratio interposed
therebetween. Feedback control is performed so as to bring an actual
air-fuel into a target air-fuel ratio at least in a predetermined
operational range on the basis of a detected value of the air-fuel ratio
sensor. Even in a range where the air-fuel ratio is made richer than the
theoretical air-fuel ratio, the target air-fuel ratio is set to be
richer, and the air-fuel ratio feedback control may still be executed.