A topology specifying apparatus 10 according to this invention includes, in a network having a tree type network topology, a route overlap determining section 4 configured to determine existence or non-existence of an overlap between a first route to a terminal having an unknown connection node and a second route between terminals having known connection nodes; and a topology specifying section 5 configured to determine a network topology based on the existence or non-existence of the overlap of the first route and the second route.