To provide an antenna having a dual band operation characteristic of efficiently operating in different frequency bands and an omnidirectional radiation characteristic of operating in each of frequency bands.

The dual band omnidirectional antenna for a wireless LAN comprises: a dielectric substance 18; a 1st conductive pattern 24 arranged on one surface of the substrate 18 and including a 1st feeder 26 arranged on the vertical center line of the substrate 18 and many radiating elements 28a, 28b, 30a, 30b in which one end of each element is connected to the 1st feeder 26 in a folded state, a part of the radiating elements is driven by a high frequency band and the other is driven by a low frequency band; and a 2nd conductive pattern 36 arranged on the other surface of the substrate 18 and including a 2nd feeder 38 arranged on the vertical center line of the substrate 18 and many radiating elements 40a, 40b, 42a, 42b each connected to the 2nd feeder 38 and arranged vertically symmetrically about respective radiating elements 28a, 28b, 30a, 30b on the 1st conductive pattern 24 as an arrangement format. In a coaxial transmission cable, its external conductor is brought into contact with a ground part on the 1st feeder 26 and its core is brought into contact with the 2nd feeder 38.