A multimode portable terminal capable of being connected to a plurality of radio communication networks of different standards, the terminal comprising: a mode selecting means which is switchable between automatic setting and manual setting for setting a priority order of mode selection information of the plurality of radio communication networks by input of a user of the terminal; a network judging means for judging which area of the plurality of radio communication networks the terminal is located based on presence of control signals peculiar to each radio communication network; a network selecting means for selecting one of the plurality of radio communication networks judged by the network judging means based on the priority order of the mode selection information set by the mode selecting means according to the automatic setting or the manual setting and connecting the portable terminal to the selected radio communication network; and an interface adapted to make the portable terminal serve as an extension module for communication by having the portable terminal associated with another interface provided for an external equipment, wherein the mode selecting means has the user select a mode selection menu displayed on a display so as to set the mode selection information, and in both a voice communication and a data communication, the mode selection menu includes at least three alternatives of "select from infrastructures", "select from contents", and "select from indexes"; in a case of "select from infrastructures", the mode selection information according to selection, made directly from the plurality of radio communication networks is set to the mode selecting means; in a case of "select from contents", the mode selection information according to selection made further from types of contents is set to the mode selecting means based on a database; and in a case of "select from indexes", the mode selection information according to selection made further from communication indexes is set to the mode selecting means based on the database. a mode selecting means which is switchable between automatic setting and manual setting for setting a priority order of mode selection information of the plurality of radio communication networks by input of a user of the terminal; a network judging means for judging which area of the plurality of radio communication networks the terminal is located based on presence of control signals peculiar to each radio communication network; a network selecting means for selecting one of the plurality of radio communication networks judged by the network judging means based on the priority order of the mode selection information set by the mode selecting means according to the automatic setting or the manual setting and connecting the portable terminal to the selected radio communication network; and an interface adapted to make the portable terminal serve as an extension module for communication by having the portable terminal associated with another interface provided for an external equipment, wherein the mode selecting means has the user select a mode selection menu displayed on a display so as to set the mode selection information, and in both a voice communication and a data communication, the mode selection menu includes at least three alternatives of "select from infrastructures", "select from contents", and "select from indexes"; in a case of "select from infrastructures", the mode selection information according to selection, made directly from the plurality of radio communication networks is set to the mode selecting means; in a case of "select from contents", the mode selection information according to selection made further from types of contents is set to the mode selecting means based on a database; and in a case of "select from indexes", the mode selection information according to selection made further from communication indexes is set to the mode selecting means based on the database.