The present invention is directed to a network system where plural equipments are connected to network, which comprises a clock source (2) for transmitting clocks and for transmitting time information every predetermined time to a group of sync equipments such as speakers (5) and a display (6), etc. which are connected to a network (1), a contents source (4) for offering contents to the group of sync equipments through the network, and a controller (3) for offering, to the contents source (4), delay time based on network delay when contents data is sent to the group of sync equipments and decode delay at the group of sync equipments in reproducing contents to realize synchronization of clock and phase between sync equipments connected to the network.