To improve the operability by providing an interface device separated from a transaction terminal and conducting 2-way communication between the interface device and the terminal in a contactless form.

An interface device 12 is provided separately from each ATM and 2-way communication is conducted between the interface device 12 and each ATM in a contactless form. A radio frequency communication method is especially used for the communication between the interface device 12 and each ATM. In order to realize this communication, the interface device 12 is provided with a transceiver 21 and each ATM is provided with a transceiver 19. The interface device 12 makes transmission by using any r a plurality of frequency bands allocated according to the RF communication regulations for industrial, scientific and medical use. Thus, it is not required to locate the interface device 12 an each ATM on a straightforward line of sight for the 2-way communication between the interface device 12 and each ATM. Moreover, the interface device 12 (each ATM) has a modem 23 (17).