To evade the decline of transfer quality received by a packet to be transmitted by performing the pseudo transmission of signals for indicating that the collision of transmission packets is generated to a communication network at the time of judging that the packet to be transmitted belongs to a packet flow to be provided with predetermined transfer quality and the transfer quality can not be satisfied by performing transmission standby.

An IP(internet protocol) packet identification part 61 identifies a flow or the like to which an IP packet to be transmitted belongs and a transmission medium monitoring part 64 monitors the state of a transmission medium and turns a frame transmission part 63 to the transmission standby when other frames are during the transmission. An IP packet schedule part 67 predicts the transfer quality of the IP packet belonging to the flow for requesting the transfer quality and transmits pseudo Jam signals through a Jam signal transmission part 66 at the time of judging that requested quality is not satisfied. The transmission of the other packets during transfer on the transmission medium is stopped and the transfer of the IP packet of the transfer quality for satisfying the request is made possible.