An image processing apparatus that enables to make a periodic noise in a captured image less noticeable without making the whole construction thereof complicated. An image pick up unit accumulates electric charges corresponding to an optical image of a target object and transfers the accumulated electric charges, and also reads them out as image signals. A control unit drives the image pick up unit to read out the image signals consecutively from the image pick up unit in a field-by-field base in such a manner so as to make the horizontal cycle of each field different from one another.