Inter-bus communication interface device and data security device

There is provided an inter-bus communication interface device capable of efficiently performing transfer of data between a plurality of devices connected to different buses, respectively. When communication data is transmitted, a first device writes the communication data into a buffer, whereas when communication control information is transmitted, the first device writes the communication control information into a register. A control circuit passes the communication data stored in the buffer to a second device, and passes the communication control information stored in the register to a second device.