To solve the problem that efficient storage/reproduction of musical data has not been performed.

This musical data storage device 101 is provided with an input/ output I/F 113 to output encoded musical data to a musical data reproducing device 102, a disk control means 111 to store the encoded musical data in the disk 110 as a copy and delete unencoded musical data from a disk 110 and an encoding/decoding means 112 to encode the musical data stored in the disk 110 by using an encoding key to be transferred from the musical data reproducing device 102 and to decode the encoded musical data which is stored as the copy by using a decoding key to be transferred from the musical data reproducing device 102 when the encoded musical data is deleted at the musical data reproducing device 102.