PURPOSE: To standardize the times of respective systems with an economical constitution by providing one system with a standard clock and a time sending means and providing the other systems with time transfer request sending means and time control means.

CONSTITUTION: One of plural systems existing in a local area network is provided with a standard clock 11 and the time sensing means consisting of a control part 103 which sends the standard time of the standard clock, an interface control part 104, etc. The other systems are provided with time transfer request sending means consisting of interface control parts 661, time request control parts 662, etc., and time control means consisting of time control parts 663 which control the times of systems themselves, etc. The system provided with the standard system sends the standard time to the system from which issues a time transfer request when receiving the time transfer request from the system which is not provided with the standard clock, and the system which issues the time transfer request receives the standard time and causes the time of the system itself to coincide with the received standard time.