A method of preventing reduction of sales amount of records due to a digital music file illegally distributed through a communication network is disclosed. The method comprises a)collecting an illegally produced digital music file, which is derived from a record of a cooperating record corporation by searching the network, b)encrypting the collected digital music file with a predetermined key; and c)redistributing the encrypted digital music file through the network. According to present invention, the method collects the illegally produced(or reproduced) digital music file that is shared and distributed through the network, encrypts the collected music file, and enables only users having a private key to use the digital music files, thus inducing the users habitually using the digital music files to use them after paying a justifiable fee and being assigned the encryption key, and to purchase the formal record.