A wireless multicasting service method using a relayed transmission scheme is provided. In the wireless multicasting service method, a mobile node moves from a first wireless network to a second wireless network. Then, the mobile node performs a new joining request to a mobile multicast agent managing a multicasting service in the second wireless network. If the mobile node receives a joining approval for the new joining request, the mobile node performs a secession request to a previous mobile multicast agent managing a multicasting service in the first wireless network.