In an image sensing system having an image sensing optical system, and an image sensing element for photoelectrically converting incoming light from the image sensing optical system, a predetermined pattern image for adjustment, which is specified in advance, is read by the image sensing element, and the image sensing element is driven to adjust its position on the basis of an output from said image sensing element, thereby adjusting the relative position of the image sensing element with respect to the image sensing optical system prior to an image sensing operation.