An image pickup apparatus detects a subject based on an image signal output from an image sensing unit and acquires a size of the detected subject. The image pickup apparatus performs an automatic zooming operation such that a zoom lens is driven so as to increase or decrease the size of the subject so that the size of the subject becomes equal to a reference size of the subject. In a case where the difference between the size of the subject and the reference size has increased beyond a predetermined threshold value and the position of the zoom lens has reached a wide angle end or a telephoto end, the image pickup apparatus resets the reference size to be equal to the current size of the subject.