A control apparatus for an internal combustion engine including a valve stop mechanism, the control apparatus comprising: an exhaust valve stop mechanism which is capable of changing an operation state of an exhaust valve between a valve operating state and a valve closed and stopped state, the exhaust valve being provided in all cylinders of an internal combustion engine having at least one cylinder; intake valve stop mechanism which is capable of changing an operation state of an intake valve between a valve operating state and a valve closed and stopped state, the intake valve being provided in all the cylinders; intake valve abnormality determination means which determines by an intake pressure sensor based on an intake pressure, by an air flow meter based on an intake air flow rate or by a valve sensor for detecting a presence or absence of an open/close motion of the intake valve, a presence or absence of an abnormality of a stopping operation of the intake valve by the intake valve stop mechanism; an air fuel ratio sensor which detects an air fuel ratio of gas discharged from each cylinder; discrimination means which discriminates a presence or absence of a change to a rich side of an air fuel ratio of the gas detected by the air fuel ratio sensor while fuel supply is stopped for all the cylinders; and exhaust valve abnormality determination means which determines that a stopping operation of the exhaust valve is not performed in a normal manner in at least one cylinder when the discrimination means discriminates that there is the change to the rich side of the air fuel ratio of the gas during a period in which the engines is rotating, in a case where it is determined that no abnormality has occurred in the stopping operation of the intake valve. an exhaust valve stop mechanism which is capable of changing an operation state of an exhaust valve between a valve operating state and a valve closed and stopped state, the exhaust valve being provided in all cylinders of an internal combustion engine having at least one cylinder; intake valve stop mechanism which is capable of changing an operation state of an intake valve between a valve operating state and a valve closed and stopped state, the intake valve being provided in all the cylinders; intake valve abnormality determination means which determines by an intake pressure sensor based on an intake pressure, by an air flow meter based on an intake air flow rate or by a valve sensor for detecting a presence or absence of an open/close motion of the intake valve, a presence or absence of an abnormality of a stopping operation of the intake valve by the intake valve stop mechanism; an air fuel ratio sensor which detects an air fuel ratio of gas discharged from each cylinder; discrimination means which discriminates a presence or absence of a change to a rich side of an air fuel ratio of the gas detected by the air fuel ratio sensor while fuel supply is stopped for all the cylinders; and exhaust valve abnormality determination means which determines that a stopping operation of the exhaust valve is not performed in a normal manner in at least one cylinder when the discrimination means discriminates that there is the change to the rich side of the air fuel ratio of the gas during a period in which the engines is rotating, in a case where it is determined that no abnormality has occurred in the stopping operation of the intake valve.