With the wide spread of the Internet and the increasing of the Internet users, the fact of concentrated accesses to a specific server becomes a critical problem and it is important to process those accesses effectively. Multihomed network is attracted much attention to provide stable and efficient Internet services. In this paper, we focus on the multihoming method in the IPv6 environment. In the IPv6 environment, each host can obtain multiple IP addresses from different ISPs on one network interface, thus the multihoming is relatively easier than that in IPv4 environment. Also, for the multihoming in the IPv6 environment neither special operations are needed in the client side nor deep technical knowledges are required to the administrator. However, since many ISPs adopt ingress filtering for security concern, a multihomed site should select a proper site-exit router according to the source IP addresses of the packets. In most site existing methods, a kind of source IP address dependent routing function is introduced which have some problems in terms of high deployment cost. In this paper, we propose a new site-exit router selection method using the routing header in the IPv6 environment. This method introduces two middle-wares, one in server that attaches a routing header which indicates a specific site-exit router, and the other in site-exit router that removes it. We implemented a prototype system and confirmed it worked well with reasonable overhead.