A router device and a frame transfer method capable of attaching a virtual identifier necessary for the datalink layer switching that improves a transfer efficiency at the router device. The router device receives a frame having a datalink flow identifier for identifying a flow of a packet corresponding to the frame on a datalink layer, which is contained in a prescribed region of the frame corresponding to an upper layer protocol identification information region of a frame format for frames to be transferred via a network layer processing, and transfers the frame received from a previous hop node to the next hop node by obtaining the address information of the next hop node by referring to the memory unit using at least the datalink flow identifier contained in a prescribed region of the frame as a key, and by attaching the address information of the next hop node to the frame, without carrying out the network layer processing, where the memory unit stores a correspondence of the datalink flow identifier and an address information of the next hop node.