A configuration performing processing of dividing a file into a plurality of pieces and transmitting the same even when a size of the file is large in transfer of files (input/output) between computers on a network is provided. A multi-thread file input/output system includes a first module performing processing of reading data from an input file, dividing the data into a plurality of pieces, and transmitting the plurality of pieces to a network by multi-thread processing in a transmitter computer; and a second module performing processing of receiving the plurality of pieces from the network and integrating and writing the same to an output file 5 in a receiver computer.