To provide a communications network that eliminates a waveform distortion of a signal between electronic control units connected to a transmission line or a branch line while having a simple structure.

A communications network 10 comprises an ECU 14a (a first electronic control unit), an ECU 14b (a second electronic control unit), a bus (transmission line) 16 connecting between the ECUs 14a and 14b, an ECU 14c (a third electronic control unit) connected to a branch line 20 branched from the bus 16 and being capable of communicating with at least either the ECU 14a or 14b. The ECUs 14a and 14b are terminated with a termination circuit 22 depending on a characteristic impedance of the bus 16 in the communications network 10, one end of a conductor wire (stub filter) 24 is connected to the branch line 20 and the other end of the conductor wire 24 is left open.