Digital Contents Services based on Internet are developing into an ubiquitous television that allows subscribers to be able to enjoy digital contents anytime and anywhere However, illegal copies and distributions of digital contents are also increasing proportionally. To guarantee the stability of contents service, many technologies are being developed and installed. The efficient scheme to manage content encryption keys is one of them. In this paper, we propose an improved key management scheme to manage the members of groups. The proposed scheme has a minimized transmission overhead for batch operation to renew content encryption keys.