An electrophotographic apparatus of the retention type is provided with a record paper detection assembly which generates a paper shortage signal when the number of record papers stored in a paper cassette is decreased to a predetermined small number substantially equal to the number of copies which can be formed from a single latent image. When the paper shortage signal is produced during a retention copy for a document, the copying operation is completed for the current document, but further copying operation for a next document is inhibited. After the copying operation for the current document has been finished, an indication lamp is lighted to indicate that the remaining number of record papers in the cassette has been reduced to the predetermined number. Further, the copying operation for the next document which has been set on a document table can be initiated automatically after the paper cassette with a sufficient number of papers stored therein has been attached to the apparatus.