A data-storing-terminal counting unit counts the number of communication terminals in which each of a number of data are stored. Based on the results of the counts, a communication terminal count estimation unit estimates the number of communication terminals that will transmit data with the same timing. An adjustment reference value calculation unit computes an adjustment reference value for constraining the number of communication terminals estimated by the communication terminal count estimation unit to be less than or equal to a preset allowable number. On the basis of the adjustment reference value computed by the adjustment reference value calculation unit, a determination unit determines whether or not to permit transmission of data stored by a storing means. If the determination unit permits the transmission of said data, a data transmission unit transmits the data to a communication terminal in which said data is not stored.