An apparatus for detecting a variation abnormality in an air-fuel ratio between cylinders according to the present invention is configured to calculate a value representing a change in an air-fuel ratio based on an output of an air-fuel ratio sensor that is provided in an exhaust passage in a predetermined operating state in which fuel is injected from a fuel injection valve, perform, to the calculated value, sensitivity correction in accordance with a sensitivity of the sensor based on the output of the sensor during fuel-cut operation and outside atmospheric pressure correction based on outside atmospheric pressure, and determine the presence or absence of a variation abnormality in an air-fuel ratio between cylinders by comparing the corrected value with a predetermined value.