To suppress delay time to wait for a processing generated for every packet, delay time to generate the packet and consumption of ATM connection and VPI/VCI.

Addresses of a transmitting origin and a destination of a network layer of the packet are detected and a kind of transport layer is discriminated by a flow detecting part 8. Connection is set for every address of the transmitting origin and the destination and every kind of transport layer when output ATM connection is set by a connection processing part 10. Consequently, delay of waiting for every packet is suppressed. In addition, cut through transfer is performed as a cell itself only when the transport layer is of a connection type. Consequently, the ATM connection and consumption of the VPI/VCI are suppressed while an advantage of the cut through transfer is utilized.