A central computer 100 is connected through communication circuits 120 with a plurality of terminal devices 110A, llOB .... such that the users of the terminal devices do not suffer disadvantages in dealing produced by differences in transmission time with respect to the central computer. Prior to ordinary processing, the transmission time required to effect information transmission between the central computer and the various terminal devices is measured. Using the result of this measurement, an adjustment time is then set in each terminal device such as to make the transmission time coincide with a reference time. When in receipt of transaction information, each terminal device displays this transaction information after the lapse of the adjustment time following physical reception. And when a transaction request is input at each terminal device, this transaction request is transmitted to the central computer when the adjustment time has elapsed after the actual time of input.