An image forming apparatus having a reading unit which reads image information on an original, a first compression unit which compresses the image information into compressed image information, a first encoding unit which encodes the compressed image information, an interface unit which acquires printing information in a page description language from exterior, a generating unit which generates printing image information on the basis of the printing information, a second compression unit which compresses the printing image information into compressed printing image information, a second encoding unit which encodes the compressed printing image information, a decoding expansion unit which decodes and expands the encoded compressed image information and the encoded compressed printing image information, and a forming unit which forms an image onto a recording medium on the basis of the image information and the printing image information which have been decoded and expanded.