An image forming apparatus includes a scanner for reading image information of an original, a memory for storing the image information of a plurality of originals read by the scanner, a printer for forming the image information of at least two of the originals stored in the memory on a single image formation medium, a detector for detecting that the memory becomes full, and a controller. When the detector detects that the memory becomes full while the scanner is performing a series of read operations, the controller controls the printer to print images of the image information of originals which are stored in the memory and images of which are to be formed on a single sheet, erases the image information whose images are printed, and controls the scanner to restart reading of the originals.