PURPOSE: To shorten a transfer time, by converting a pattern 0000 to a character, and utilizing effectively a space compression function.

CONSTITUTION: An original data in a data file DF1 is fetched by a 4 bit unit, is converted to a character space in case of 0000 by a hexadecimal-converting means 1, is hexadecimal-converted in other case than 0000, and is converted to characters 1W9 and AWF. Subsequently, the character space, 1W9 and AWF outputted by the means 1 are subjected to space compression by a data transfer terminal 2 and are transmitted. The receiving side receives the transmitted information by a data transfer terminal 3, releases the space compression, and converts it to the character space, 1W9 and AWF. Subsequently, these characters is brought to hexadecimal reverse conversion 4, and an original data is regenerated by reverse-converting to 0000 and 0001W1111 in case of the character space, and in case of the characters 1W9 and AWF, respectively.