An external connection interface emulation method and apparatus of a mobile terminal for exploiting the mobile terminal as a network adaptor of another terminal are provided. The external connection interface emulation apparatus includes a network modem for supporting communication through the mobile communication system; and a controller, which configures the network modem for operating the mobile terminal as an external network adaptor of another terminal or a communication device as it is, according to an input signal. The external connection interface emulation apparatus and method establish a communication link between a WiBro modem and a USB port at the software level making it possible to use the mobile phone as an external modem regardless of whether the WiBro modem and the USB port are compatible or not.