To optimally control an operating frequency of a CPU while ensuring real-time property for event processing in a real-time system for handling a plurality of tasks.

In a configuration for supplying power to a processor, there are provided a task request performance table 22 for storing performance solely requested by a task; a power mode table 25 determining an operating frequency of a processor that executes required system request performance; a system request performance calculation block 21 for calculating a system request performance by adding performance requested by several tasks when some tasks perform execution request in the same period; and a power mode determination block 23 which calculates new system request performance by adding processing requests at a time point of a processing request when there are processing requests from tasks, sets the operating frequency of the processor, and continues setting of the operating frequency when there is a residual tasks when a task completes processing, or turns the system request performance into most power saving mode when there is no residual task.