PURPOSE: To omit information capacity transmission performed separately from transmission for confirming whether the transmission is normally completed or not by integrating the information capacity of a data file to be transmitted into the data file name.

CONSTITUTION: A transmission side system 1 generates the data amount of a file from a data file A4 of a transmission object and integrates the value of this data amount into the file name of data to be transmitted in the form of the data file A-the data amount. Next, the generated file name and the data in the data file A4 are transmitted to a reception side system 2 by a data transmitting means 3. The reception side system 2 generates a data file a5 from the transmitted data. At such a time, the file name in the transmitted data and the form of the data file A-the data amount are used for the file name of the data file a5, the value of the data amount integrated into the file name is compared with the data amount of the generated data file a5 and corresponding to whether they are coincident or not, it is judged whether the transmission is normal or not.