A packet rewriting apparatus is arranged between a tunnel end point and a switch that refers to content of the original header to determine processing to be applied to a packet. The packet rewriting apparatus is provided with: a packet rewriting rule storage unit that stores packet rewriting rule(s) for writing information corresponding to a virtual network identifier included in an additional header of a packet outputted from a tunnel end point, to a prescribed region of the original header; and a packet rewriting unit that rewrites, in accordance with the packet rewriting rule, to a packet in which information corresponding to the virtual network identifier is written to the original header of a transmitted packet.