1. An event processing apparatus comprising: a memory including an event queue that temporarily accumulates a plurality of events when occurring and including a task queue that temporarily accumulates a plurality of tasks relating to the plurality of events read out from the event queue; task execution means for executing a task read out from said task queue; task execution time memory for receiving a task execution time from said task execution means, and for storing a mean execution time corresponding to a task identifier; central-processing-unit (CPU) load calculation means for using said task execution time memory to calculate a CPU load by dividing a sum of mean execution times for all unexecuted tasks accumulated in said task queue by a CPU processing time unit; and event queue optimization means for executing, depending on the CPU load, filtering processes to delete one or more events based on optimization definition information, and/or chunking processes to integrate a plurality of events accumulated in the event queue into one event based on the optimization definition information.