PURPOSE:To contrive the unifying of the time for each system in the local area network with an economical constitution by providing a standard clock and means sending its standard time to other system at a prescribed interval to one system and providing a means controlling the time in its own system to the other system. CONSTITUTION:The home system 1 among plural system of the network is provided with the standard clock 11 and a time sending means composed of a time transmitting control section 103, etc., sending the standard time at a prescribed interval. Moreover, the other system is provided with a time control means (office computer 66) composed of a time reception control section 662 and a time control section 663, etc. Then the system 1 sends the standard time at every prescribed time and the other system not having the standard clock receives the standard time to make the time of its own system coincident with the received standard time. Thus, the time in the local area network is made unified surely.