Recent proliferation of Wireless LAN devices has created a high demand for roaming systems that enable network connections at visited institntions using users' home accounts. We have been operating eduroam, the roaming system for international research and edncational institutions. However, if the roaming system is to be introduced into more than a thousand of research and educational institutions in Japan, some operational and management difficulties arise at each institution as well as at the eduroam national operational body. In this paper, we propose a centralized delegate authentication system using pseudonymous ID for reducing operational cost and for protecting user's location privacy. A prototype system using Shibboleth is also presented.