To provide the data storage device where recorded data can freely be reproduced and observed without stopping recording of data supplied for display, and to provide the data communication system and the storage medium.

A video server in a video conference system records data of conference contents sent/received via a communication line in a hard disk (S1). Furthermore, the video server divides data denoting the conference contents into data for each one second in time series and records the divided data to the hard disk as different files 'TEMP1', 'TEMP2',... 'TEMPn' (S3, S7). Thus, the recorded data can freely be read without stopping recording processing.