PURPOSE: To facilitate a switching to an optimum antenna depending on the operating condition by adopting the cassette type for antennas such as a case build-in antenna attachably and detachably to/from a radio input/output terminal of a radio equipment, a unipole antenna or a gain antenna.

CONSTITUTION: Part of a radio equipment main body l of a portable radio equipment is cut off and a mount section 8 having the radio input/output terminal 7 is provided. An optimum antenna is selected among a cassette antenna 2 or various antennas, connectors 6,7 are fitted together and a cassette antenna is mounted to the mount section 8. Since the cassette type antenna is mounted to the part of the radio equipment main body while being replaced in this way and the antenna most suited to the purpose and shape of the operation is mounted in the best state of the antenna, the rational use is attained especially in combination with a portable radio equipment.