Transmission line groups consisting of a plurality of loop-like transmission routes are mutually connected via transmission controllers, and are arranged on a two-dimensional or three-dimensional space. Therefore, processing units are connected as a homogeneous network in the matrix or mesh form by means of the loop-like transmission routes. The transmission controllers corresponding to the nodes of the network have a communication management function such that they send the data without grasping the situation on the transmission routes, independently check the trouble between the adjacent transmission controllers and specify the position of trouble. A communication network system such as a high local area network (LAN) or the like can be realized.