PURPOSE: To prevent the deterioration of a characteristic owing to the invasion of static electricity occurring by contact with a human body in a watch-type portable radio machine.

CONSTITUTION: A loop antenna is constituted by connecting a pair of antenna boards 5a and 5b in the watch-type portable radio equipment by an inside clamping ring 4. The tuning circuit of the antenna is formed by a pair of varactor diodes 10 and 11 which are connected to the loop antenna in parallel. The middle point of the varactor diode is connected to the positive electrode of the power battery 8 in the radio machine through a resistor 16, and it is electrically connected to a back cover 2 consisting of a conductive member. Furthermore, the antenna board 5a is electrically connected to the back cover 2 consisting of the conductive member which is set to the positive potential of power voltage through a resistor 17 at an intersection point with a capacitor 9a.