In order to provide a technique in which, in the TEM type antenna, the uniformity of sensitivity in the internal portion of the antenna can be maintained with simple configuration, without scarifying the internal space of the antenna, regardless of a size, a shape and a location of a load, and also regardless of locations of the constitutional members of the antenna, the TEM type antenna includes rung conductors which branch out into plural pieces in the middle portion and join into one piece in the two end portions. In other words, the rung conductor having a void space in the middle portion of the rung conductor in the longitudinal direction is provided. The adjacent rung conductors are disposed to be further closer to each other in the middle portion, and to maintain the same distance as that in the related art in the end portion.