PURPOSE: To improve the performance of timer control in a virtual computer system by using a timer control part by plural operating systems in common and executing a timer instruction and timer end processing only by one stage.

CONSTITUTION: The timer control part 5 including a timer control table 52, a timer instruction executing means 50 and a timer end informing means 51 is used for respective operating systems in common by a sharing means arranged in a system sharing address space, a timer connected to a computer system is unitedly controlled and timer requests from plural virtual computers α, βare unitedly processed. Since a timer instruction and timer end processing can be executed only by one stage, the performance of timer control in the virtual computer system can be improved.