An image forming apparatus in which a memory has a first storage area for storing information related to image formation as predetermined unit data and a second storage area (back-up memory) for storing the information as bit-unit data. A printer control unit, which controls writing/reading of the information related to image formation to/from the memory, stores the information related to image formation, stored in the first storage area as the predetermined unit data as the bit-unit data, into said second storage area.