Recently, wireless network services are available at a variety of public spaces such as stations, airports, and hotels. In such services, the IEEE802.1X-based authentication protocol has been often used to permit only registered users in network connections. However, this protocol allows Internet service providers (ISPs) to collect the privacy information of users such as their access locations and network service use records. Besides, ISPs have to keep in secret the personal information of their users for authentication, although they only need the legitimacy of them. To solve these problems, this paper presents an anonymous authentication protocol based on IEEE802.1X. The group signatur e scheme is adopted to anonymously verify the legitimacy of users, whereas misbehaving users can be traced in case. We implement the proposed protocol by modifying open source softwares for IEEE802.1X and verify the effectiveness in terms of the processing time and the packet size.