PURPOSE: To prevent the malfunction of jobs by providing a job abort flag/abort flag setting means, a forcible end range judging means, a job forcible end means, and a task forcible end means.

CONSTITUTION: An abort flag setting means 3 turns on a job abort flag 1 when the designation is previously applied so as to forcibly end a job when a task used a CPU until the limit time. A forcible end range judging means 4 refers to the flag 1 when the task used the CPU up to the limit time and transfers the control to a job forcible end means 5 when an ON state of the flag 1 is decided. The means 5 ends forcibly a main task including the task that used the CPU until the limit time and then refers to a task control structure 2 to end the processing if no subtask is included in the job. Thus it is possible to prevent the job malfunction due to a fact that a task used the CPU until the limit time and was forcibly ended.