The time of transmission and reception between stations A and B is exchanged, and any deviation in time is calculated in a corresponding manner in the stations. Using the transmission time TXA from station A to B, the transmission time TYB from station B to A, the time TXB of a clock at station B in a transmission from station A to station B, and the clock time TYA at station A in a transmission from station B to A, the following are measured in sequence: 1) station A records the time TXA at which TXA and TYA were transmitted, 2) station B measures the time TXB at which TXA and TYA were received, 3) station B records the time TYB at which TXB and TYB were transmitted, and 4) station A measures the time TYA at which TXB and TYB were received, the transfer time between stations A and B being derived at each station on the basis of the average of the increase ΔTXB-A from TXA to TXB and the increase ΔTYA-B from TYB to TYA, or the deviation in time for a transfer between stations A and B being determined by subtracting the increase ΔTXB-A from the transfer time. The transmission time TXA from station A to B may also be measured using a reflection signal from a transmission terminal.