Compression-decompression functions provided in the recording device are easily replaceable so that they conform with the compression-decompression function provided in the host computer. A recording device 10 connected with a host computer 20 for operation based on commands from the host computer 20 comprises a interface card 12 mounted in the recording device 10 replaceably with respect to the control board 11 for exchanging data with the host computer 20. A first data decompressor 30 is included in the interface card 12 for decompressing compressed data to be exchanged between the host computer 20 and recording device 10. This allows selection and replacement of decompression function in the recording device in conformance with the compression algorithm in the host computer without replacing the recording device as a whole.