To provide a portable radio terminal device that effectively avoids communication error or the like due to antenna characteristics deterioration due to a transmission antenna being covered by user's hand and head.

A first transmission antenna 2 and a seconding transmission antenna 3 are arranged at the lower part and the upper part respectively of a housing 1. Either of a pair of the transmission antennas 2 and 3 is used as a normally used antenna, and a sensor 8 is arranged in the vicinity of the transmission antenna. When the 1st transmission antenna 2 is covered by user's hand 4, a control signal is sent to a controlling part 6 to automatically change an antenna changeover switch 7 to the second transmission antenna 3.