To improve a compression rate by means of binary compression and to make storage or transportation efficient.

The compression method of MIDI data compresses data following an MIDI rule. MIDI data of one sound on MIDI data of plural sounds are dissolved into the five elements of the pitch of sound, an interval with next sound, the length of sound, the loudness of sound and a channel number. A rearranging processing for re-connecting the sounds for the respective dissolved elements is executed and binary compression by a Huffman encoding method and an LZ77 encoding method, for example, is executed.