In image signal storing method and apparatus, a continuous tone image signal representing a continuous tone image and a binary image signal representing a binary image, which carries information giving specifics about the continuous tone image, are obtained. A redundancy imparting process is carried out on the binary image signal in accordance with irreversible signal compression processing such that the information represented by the binary image signal may not be reduced when the irreversible signal compression processing is carried out. Thereafter part of the continuous tone image signal, which part corresponds to part of the region in the continuous tone image, is replaced by the binary image signal, which has been obtained from the redundancy imparting process. The irreversible signal compression processing is then carried out on an image signal, which has been obtained from the replacement. An image signal, which has been obtained from the irreversible signal compression processing, is then stored.