In order to effect an automatic focus control in an image pick-up apparatus, a photography lens for forming an image of the object onto a two-dimensional solid state image sensing device is arranged in a fixed position, while the two-dimensional solid state image sensing device is arranged movably in the optical axis direction of the photography lens, and the image sensing device is moved in accordance with a focusing error signal detected by a focusing condition detecting circuit having an additional light receiving element mounted on the same substrate as the image sensor but discrete from and operating independently of the image sensor. Since the light and small solid state image sensing device is moved for the focus control instead of the heavy and large photography lens, it is possible to perform the focus control in a prompt manner and to make a mechanism for driving the image sensing device small and simple.