Abstract: A slit exposure scanning type electrophotographic copying apparatus has an optical system enclosed in an optical frame within which a light source for illumination, an image transmitter formed by a bundle of optical fibers of graded refractive index, and other associated elements are secured in predetermined relative positions with the optical frame urged to engage a movable or stationary transparent platform for placing an original to be copied for easy focusing and positioning adjustments in assembling the copying apparatus. The concept of the optical frame is applicable both to a copying apparatus with a moving platform and a stationary optical system, and one with a stationary platform and a moving optical system irrespective of whether it is a wet-copying process type or dry-copying process type.