To provide an image management method capable of efficiently retrieving location, even if an interrupt occurs at the image processing, in an information retrieval system.

A location information PID is appended to each output image, in the order of image processing. The location information PID, appended to each output image, is associated with image ID information GID_G for uniquely identifying each job and is registered in a database DB. Since job execution sequence is changed when processing is interrupted/resumed, the location information PID is given to each page image, in a discontinuous order. When a certain location information PID is extracted from an output image to use it as a retrieval condition at the time of retrieval processing, other location information PID, associated with the same thing as the image ID information GID_G related with the extracted location information PID, is to be retrieved.