A copying apparatus comprises a document glass, an automatic document feeder that is free to be opened and closed with respect to the document glass, a paper feeding means, means for storing image formed papers and an image forming means. The image forming means is operable in a special paper-passing mode that permits the transfer paper to be ejected into the storing means without having the image formed thereon. The copying apparatus is provided with means for detecting the open and close actions of the automatic document feeder so that an alarm can be issued to remind the operator of the document left on the document glass according to the signal issued by the detecting means after the operation of the image forming means has been completed, and the operation of the alarm means can be inhibited after the operation of the image forming means in said paper-passing mode has been completed.