PURPOSE: To enhance the communication efficiency of the entire network by controlling a communication control parameter from collected communication information on a transmission medium dynamically in details.

CONSTITUTION: A communication state on a transmission medium 3 is always monitored by a monitor block 10 and the data is stored in a register block 11. A command block 12 generates command information to increase the communication efficiency of a network for a general station 2 and sends the information to the station based on the data stored in the block 11. Upon the receipt of the command information from a management station 1 by a reception block 20 of the general station 2, a revision block 21 revises a communication control parameter based on the command information. For example, when number of times of failed transmission to a specific station is very much, whether the cause resides in a transmission medium or in the station itself is discriminated from the operating state of the entire network. When it is discriminated that there is a problem in the On the other hand, of the station, the processing such as a request of the transmission of the current operating state or the revision of the communication control parameter of a relevant station is attained.