PURPOSE: To improve the throughput of a process controller by counting the generating times of notifying signals in order to notify a process with which a program is over and also to reduce the count value by one unit if the notifying signals are produced after reception of an interruption request in a multi- task system.

CONSTITUTION: An interruption detecting part 2 detects the notifying signal received from a CPU with an external interruption request. A state deciding part 4 scans the process of a queue train 3 based on the detected notifying signal and applies the notifying signal to the process which is not kept in a run state. Meanwhile a notifying unable signal is outputted when all processes are kept in the run states. A counter 5 counts these notifying unable signals. When a processing end detecting part 6 detects the end of a process program, a remaining interruption deciding part 7 reduces the count value of the counter 5 by one unit and at the same time notifies again the process whose program has just ended.