A core switch in a QinQ model receives frames having different IVIDs but having the same transmission source MAC address in some cases, and therefore a problem of MAC duplication occurs in the core switch. To solve this problem, this flow processing device is characterized by being provided with: an MAC address table 420 in which an MAC entry is registered; an MAC duplication table 490 in which in response to the updating of transmission destination information of the MAC entry on the basis of a received frame, a duplicate entry including information related to the frame is registered; and an access list table 450A in which in response to the registration of a plurality of duplicate entries related to each other in the MAC duplication table, a transfer entry for transferring the frame related to the plurality of duplicate entries is registered, wherein the frame related to the plurality of duplicate entries is transferred in accordance with the transfer entry.
