At a data receiving terminal, if a received-data of a particular time section received from a data sending terminal does not satisfy a predetermined accumulation quality as the result of discrimination by a received-data quality discriminating section, an alternative-data sending requesting section requests a data sending terminal for alternative data satisfying the accumulation quality for the unsatisfied data of the particular time section. The result is that the data receiving terminal can realize both reproduction of data with less sending delay and accumulation of high-quality data.