PURPOSE: To execute quickly the selection of a task which is executed in the next time, also to increase a chance for executing the task, and to execute uniforminly a processing by generating a queue by connecting only the task which can be executed.

CONSTITUTION: A timer mechanism initializing part 1 sets an initial value to a timer for controlling a priority degree of a task. When an interruption is generated in a timer interruption generating part 2, a timer interruption processing part 3 starts a priority degree controlling task. An execution queue managing part 4 connects the task to an execution queue, based on a task execution priority degree. In a dispatch control part 5, the task is selected in order from the execution queue whose task execution priority degree is the highest and a use right of a CPU is given. A priority degree controlling task 6 checks a queuing time with regard to the task except the execution queue of the highest task priority degree, and raises the task execution priority degree by one after a prescribed time has elapsed.