PURPOSE: To improve the antenna characteristic by winding an inner conductor wire in spiral so as to make the pitch dense and winding a flexible outer conductor wire on an outer side between the pitches of the inner conductor wire in spiral.

CONSTITUTION: The antenna 3 consists of a flexible inner conductor wire in which an inner stainless steel wire 9 whose cross section is circular is wound in spiral with a dense pitch and of a flexible outer conductor wire in which an outer stainless steel wire 11 whose cross section is triangle is wound in spiral onto an outside between pitches of the inner side stainless steel wire 9. Moreover, the antenna 3 is made removable from a case 7 by means of a connector 5. Thus, even when the antenna collides with a human body, the safety is improved and the antenna characteristic is improved regardless of the attitude of the case.