The present invention aims at providing a communication apparatus accommodating both a LAN line or a broadband line and an ordinary public network (PSTN) so as to enable the simultaneous use of two lines according to two network connection methods by using a single physical line capable of accommodating the high-speed line and the public network.There are provided an IP phone having an interface for connection to an Internet line and an analog telephone having an interface for connection to a PSTN line. A control section selects an Internet telephone or a public network telephone to be used. While one telephone line is busy, the other idle line is used for communication.