This invention has as its object to provide an ATM relay device which attains high-speed, large-capacity packet relaying by distributing the load on an IP forwarding unit without having to improve the operation speed, processing performance, and the like of an IP forwarding function. This invention has an ATM switch core (111) for distributing input ATM cells to corresponding ones of a plurality of output ports on the basis of their destination information. A plurality of IP forwarding units (120-1 to 120-n), which are provided in correspondence with the respective output ports of the ATM switch core (111) and have unique forwarding processing functions, execute predetermined forwarding processes for packets obtained by reassembling ATM cells input via the respective output ports. An SAR 121 assigns destination information that assumes different values in units of packets to ATM cells, which form each of packets having an identical address of those processed by the plurality of IP forwarding units (120-1 to 120-n). The ATM cells of a packet assigned identical destination information by the SAR 121 are stored in a PerVC queuing unit 112 by a predetermined volume, and are output in the format that stores the ATM cells by the predetermined volume.