In a zoom camera having a zoom lens including a variator lens, and a driving system for driving the variator lens, the image magnification is computed in accordance with a predetermined program based on the detected object distance, and such a focal length is computed as to obtain a specified value of image magnification based on the detected object distance and the computed image magnification, and the obtained focal length data is fed to the driving system. As a result, auto-zooming with a suitable image magnification in accordance with the object distance can be achieved.