PURPOSE: To enable classification corresponding to the priority of queues to be executed and queues having various attributes in the same class to be set by comparing the priority of a queue, of which priority is registered in a job, with the priority of a job registered on the other queue having the same priority, and deciding the order of execution, without closing the queues, of which priority is registered in the job.

CONSTITUTION: A queue priority managing part 1 investigates which queue is to be started to be scheduled with, selects a queue '1' having the most significant queue priority, investigates whether the job to be selected for being executed is still registered on the queue '1' or not, selects the queue '1' as the object of schedule and informs a job priority managing part 2 of it. The job priority managing part 2 decides the job to be executed by comparing the priority of all the jobs in the candidate key. When the job to be executed is decided, that job is executed by a job execution part 3. Thus, the queues are successively selected, and the job having the higher priority is executed.