Abstract: A packet transmitting method of processing a packet having a control information area and a user information area by a functional block in a node and, thereafter, transmitting the packet from the node. Whether information of the user information area is useless for the user or not is discriminated on the basis of information of the control information area or the user information area. The packet judged to be useless is converted into a predetermined format in which the number of alternating times of a bit pattern has been reduced and the packet is allowed to pass through the functional block. The bit pattern of the packet is returned to a state before the conversion at least before the packet is transmitted from the node.