In this paper, a group signature scheme committing the group itself is proposed. In normal group signature schemes, a group member can anonymously sign a message on behalf of a group, and the anonymity of the signature can be revoked by only a designated authority. Consider a situation that multiple groups exist. In the proposed scheme, the signature hides not only the identity of the signer, but also the identity of the group. The group can be specified by only the designated authority. This characteristic is useful for a user's committing his attribute in the application to anonymous statistical surveys of users' attributes. Another application is the anonymous authentication of the membership with the expiration.