A copying apparatus has an original size sensing switch for sensing the size of an original, a memory for storing cassette size information, a comparator for comparing the original size information output by the original size sensing switch with the cassette size information read out from the memory, and a microcomputer for controlling the copying operation of the apparatus in accordance with a comparison output from the comparator. The copying operation may be performed in accordance with the size of the original fed to the exposure position. The automatic copying operation in accordance with the sensed original size may be released as needed for manual control.