A unit-type copying machine comprising an upper unit having an optical system for exposing a document to light by scanning, and a lower unit provided independently of the upper unit and having a photoconductive drum to be exposed to an image of the document projected thereon from the optical system. The upper and lower units are provided with connecting portions for detachably connecting the two units together and positioning portions for positioning the optical path of projection of the document image from the optical system in coincidence with an exposure station for the drum. The upper or lower unit is usable with selected one of different types of lower units or of different types of upper units in a suitable combination.