PURPOSE: To constitute a large-sized switching network and to transfer a variable length data packet at a rate of 1 to 1 and as a groove by forming one kind of router module as a reference constitutional element and combining the constitutional elements.

CONSTITUTION: Four-input/four-output router modules 31∼316, 41∼416, 61∼616 are formed in the switching network and input terminals 11∼164 are connected to respective modules 31∼316. Output terminals 21∼264 are connected to respective modules 61∼616 and the output terminals of the modules 31∼316 are connected to the input terminal of the modules 41∼416 through signal lines 511∼51616. The modules 61∼616 are connected to the output terminal of the modules 41∼416 through signal lines 711∼71616. Switches for guiding data inputted to respective modules 31∼316 to optional output terminals, a decoder for decoding the inputted data packet and for specifying the transfer of the decoded data packet to respective output terminals, an encoder for priority interruption, etc. are arranged to transfer the variable length data packet at the rate of 1 to 1 and as a group.