A buffer (32) for temporarily storing a packet is installed in a packet order control circuit (12H). A comparison circuit (31) compares the packet ID of an input packet with a next-selection ID indicating the packet ID of a packet to be selected next in accordance with an order. If the comparison result indicates that the packet ID and the next-selection ID do not match, a control circuit (36) stores the input packet in a storage position corresponding to the packet ID. If the packet ID and the next-selection ID match, the control circuit (36) selects the input packet as a target of a transfer process without storing the packet in the buffer (32). If the next-selection ID matches the packet ID of a packet stored in the buffer (32), the control circuit (36) selects the packet as a target of the transfer process. This guarantees the packet processing order with few memory resources.