To deal with even the case that a transfer rate is improved with small-scaled hardware resources by providing a mechanism for dividing a packet into fixed length cells at a transmission source, transmitting the cells, reconstituting and re-aligning the packet as original at a transmission destination.

A first means and a second means are included. The first means includes: a mechanism for distinguishing cells for the unit of a packet in accordance with a specific identifier; a mechanism for acquiring an address of a memory for primary storage of the packet for each packet; a mechanism for writing a cells in the memory of an address obtained by adding a cell number to the address; a mechanism for counting the number of arrival cells for each packet; a mechanism for determining that the packet is prepared in the case that the number of arrival cells matches the number of packet constituting cells; and a mechanism for recording the number of arrival cells and the memory address for each packet, wherein a packet is reproduced from cells arriving at random. The second means sorts packets from a group of reproduced packets into a group to reorder the packets in accordance with the specific identifier of the packets and realigns the packets in order as original for each group.