A header processing unit divides each received packet into a header section and a data section. Adapter memory stores each packet. A packet reassembly processing unit generates a new header, based on the header section of each of the plurality of packets and notifies a host computer of the new header and a plurality of pieces of location information indicating the storage position of each of a plurality of data sections stored in the adapter memory. A DMA control unit reads the plurality of data sections from the adapter memory, according to a transfer instruction generated in the host computer, using the location information and transfers it to the host computer.