To perform analog input-output without using dedicated commands, a device driver, etc., by mounting analog input and/or analog output devices on an external device.

This analog input-output device 10 has a digital I/O 12 which transfers digital data from/to the external device such as a personal computer, an analog I/O 16 for the input-output of analog signals, a D/A for converting and A/D converting part 15 which converts analog signals into digital signals and digital signals into analog signals, a CODEC 14 for performing encoding and decoding, a memory 11 and a controlling part 13. The part 13 performs analog input/output by using a data writing command being the existing file access command from the device 90 and a data writing command through the I/O 16.