A cylinder-to-cylinder variation abnormality detecting device including a rotational fluctuation detecting module that detects a rotational fluctuation among cylinders of a multi-cylinder engine; a rotational fluctuation type abnormality determining module that determines whether a cylinder-to-cylinder variation abnormality is occurring, from the rotational fluctuation; an air-fuel ratio detecting module that detects an air-fuel ratio; an air-fuel ratio fluctuation type abnormality determining module that determines whether the abnormality is occurring, from a fluctuation in the air-fuel ratio; a frequency component type abnormality determining module that detects whether the abnormality is occurring, from a particular frequency component corresponding to one engine combustion cycle; and a cylinder-to-cylinder variation abnormality determination finalizing module that finalizes a determination of the abnormality, if the rotational fluctuation type determining module determines the abnormality and the air-fuel ratio fluctuation type abnormality determining module determines no abnormality.