A dispatcher stack is allocated to each of a plurality of processors sharing a run queue. Each processor, in process dispatch processing, saves in a switch-source process stack the context of a switch-source process (the process being run), saves in the dispatcher stack of each of the processors a dispatcher context, inserts the switch-source process into the run queue, removes a switch-destination process from the run queue, and, in addition, restores the context of the switch-destination process from the switch-destination process stack.