According to the present invention, during the execution of a series of processes in an ordinary program, if a process being executed is suspended by the interrupt of another process, it is judged, upon completion of the execution of the interrupt process, whether a return to the above suspended process in the ordinary program is to be made or a branch return to another process is to be made, depending on the result of the interrupt process. Consequently, if the resumption of the suspended process in the ordinary program becomes no more necessary depending on the result of the interrupt process, another required process can be initiated immediately without resuming the unnecessary process.