An air-fuel ratio control apparatus which controls an air-fuel ratio of an internal combustion engine based on an output of an upstream air-fuel ratio sensor provided in an exhaust passage to be located upstream, with respect to an exhaust gas flow direction, of an exhaust purification catalyst for purifying exhaust gas discharged from cylinders of said engine and based on an output from a downstream air-fuel ratio sensor provided in said exhaust passage to be located downstream of said exhaust purification catalyst with respect to said exhaust gas flow direction, said air-fuel ratio control apparatus comprising: a determination section configured so as to determine whether or not said output (Voxs) of said downstream air-fuel ratio sensor falls within a predetermined range whose center corresponds to a target value (Voxs_ref) corresponding to a stoichiometric air-fuel ratio; and a reverse direction correction introducing section, operable when said output (Voxs) of said downstream air-fuel ratio sensor falls within said predetermined range, configured so as to temporarily introduce an air-fuel ratio correction in a reverse direction opposite to a direction requested by said output; characterized in that said reverse direction correction introducing section is configured so as to introduce a rich spike to said air-fuel ratio of said engine in a case where said output (Voxs) of said downstream air-fuel ratio sensor shifts to a rich side so that an air-fuel ratio correction in a lean direction is requested, and so as to introduce a lean spike to said air-fuel ratio of said engine in a case where said output (Voxs) of said downstream air-fuel ratio sensor shifts to a lean side so that an air-fuel ratio correction in a rich direction is requested; and said reverse direction correction introducing section is configured so as to prohibit said introduction of said air-fuel ratio correction in said reverse direction until a predetermined period of time elapses after said output (Voxs) of said downstream air-fuel ratio sensor has changed between rich and lean sides, and so as to implement said introduction of said air-fuel ratio correction in said reverse direction after a lapse of said predetermined period of time. a determination section configured so as to determine whether or not said output (Voxs) of said downstream air-fuel ratio sensor falls within a predetermined range whose center corresponds to a target value (Voxs_ref) corresponding to a stoichiometric air-fuel ratio; and a reverse direction correction introducing section, operable when said output (Voxs) of said downstream air-fuel ratio sensor falls within said predetermined range, configured so as to temporarily introduce an air-fuel ratio correction in a reverse direction opposite to a direction requested by said output; characterized in that said reverse direction correction introducing section is configured so as to introduce a rich spike to said air-fuel ratio of said engine in a case where said output (Voxs) of said downstream air-fuel ratio sensor shifts to a rich side so that an air-fuel ratio correction in a lean direction is requested, and so as to introduce a lean spike to said air-fuel ratio of said engine in a case where said output (Voxs) of said downstream air-fuel ratio sensor shifts to a lean side so that an air-fuel ratio correction in a rich direction is requested; and said reverse direction correction introducing section is configured so as to prohibit said introduction of said air-fuel ratio correction in said reverse direction until a predetermined period of time elapses after said output (Voxs) of said downstream air-fuel ratio sensor has changed between rich and lean sides, and so as to implement said introduction of said air-fuel ratio correction in said reverse direction after a lapse of said predetermined period of time.