To effectively use a band in a communication line in which a plurality of communication apparatuses are cascade-connected.

An up-link transmitting and receiving buffer unit 121 is equipped with a receiver buffer, and holds an up-link frame received from a lower-order device. A remaining buffer capacity determination unit 122 monitors the amount of remaining capacity of the receiver buffer of the up-link transmitting and receiving buffer unit 121, and determines whether there is a predetermined amount of free space or more in the receiver buffer. A stop/release code insertion unit 123 inserts a stop code in an idle period of down-link data, when the free space of the receiver buffer has reached the predetermined amount or less. A stop/release code detecting unit 125 monitors the idle period of the down-link data input to a down-link transmitting and receiving buffer unit 124, and detects the stop code from the idle period. The up-link transmission control unit 126 stops transmission of the up-link frame, when the stop code is detected by the stop/release code detecting unit 125.