To provide an Internet environment buildup set and its buildup method or the like by which an Internet environment utilizing a LAN is easily built up in a short period independently of a communication infrastructure.

A Home PNA(Home Phone Networking Alliance) unit used to build up an Ethernet (R)LAN by using an existing telephone line is installed in each house of a apartment and a phone and a personal computer are connected to the home PNA unit 9. A home PNA unit 14 is installed for each house around a line concentration box 4 of a telephone line of this apartment, to which the telephone line 6 of each house is connected. The home PNA units 14 are interconnected on the basis of the Ethernet protocol to build up the Ethernet LAN. The build-up Ethernet LAN is wirelessly connected to a relay base 2 where the connection to the Internet is ensured via a router 15. The wireless connection is attained through wireless communication between a wireless transmitter-receiver 16 at the LAN side and a wireless transmitter-receiver 17 at the relay base 2.