A communication traffic control system of this invention is directed to reduce traffic on a LAN. In LAN (1) of a CSMA/CD type having a server computer (2), a first client computer (3), a second client computer (4) and other third, fourth . . . client computers connected thereto, when the first client (3) generates a transmission request A of an object to the server (2) and receives an object A corresponding to the transmission request A from the server (2), the second client (4) stores the transmission request A and the object A corresponding to the former in a storage unit (41) inside the second client (4). When the second client (4) thereafter generates a transmission request A for acquiring the same object A stored in the storage unit (41) to the server (2), it directly acquires the object A from the storage unit (41) without it passing through LAN (1).