To provide a digital data communication method and a digital data communication device by which data transfer can be performed by radio through a digital data radio communication line network consisting of a PHS network connected to the internet network by converting all data such as data from data communication terminals, voice data from voice communication terminals such as telephones, FAX data from FAX communication terminals and the like into digital signals by an indoor device.

The digital data radio communication line network is constituted of a digital PHS network which can be connected to the internet network and an interface access unit is composed of a digital PHS access unit connected to the digital PHS network and a terminal adaptor. Data from a data communication terminal and voice data from a voice communication terminal and FAX data from a FAX communication terminal is connected to the interface access unit and all the data is communicated through the interface access unit by the digital data radio communication line network. Consequently, costs can be reduced and the office environment can be improved.