A control signal used to write access or read access and data are transmitted between a write/read unit and a memory module by a contactless coupling using induction coils. The write/read unit multiplexes a control signal consisting of three signals including a power source signal, sync clocks, and enable clocks using frequency modulation and supplies the resultant multiplexed signal to one end of the induction coil for transmission. The write/read unit frequency modulates access data and supplies same to the other end of the same induction coil for transmission. The transmitting coil in the memory module allows the signal which is obtained by adding an access signal to the control signal to be induced in the coil for reception in the write/read unit. The read data from the memory module is frequency modulated and sent from the memory module to the write/read unit by using the transmitting and receiving coils for a down-signal which is used only to read out data.