A job log collection unit cooperates with job log management programs of copying machines to collect job logs held in the copying machines and store the collected job logs in a job log storage unit. A user change history creation unit refers to a human resource database to thereby determine whether a section which each user belongs to has been changed or not in a range of newly collected job logs. The user change history creation unit creates a user change history for each user who has encountered the change and stores the user change history in a user change history storage unit. A job log aggregation unit classifies the job logs of the job log storage unit into user sections by referring to the user change history of the user change history storage unit and aggregates the job logs in accordance with each section.