The present invention discloses a broadband antenna, which comprises a radiation conductor, a grounding plane and a feeder cable. The radiation conductor has an inverse V shape. The radiation conductor has an elbow portion; a first leg and a second leg respectively extend from the elbow portion toward two different directions. A terminal of the second leg connects with the grounding plane. The feeder cable has a central wire and an external wire. The central wire connects with the second leg. The external wire connects with the grounding plane. The present invention is characterized in that only a single inverse V-shaped radiation conductor is enough to generate a baseband resonant mode and a frequency multiplication resonant mode for the antenna system, and that the present invention has a simple structure and needn't use a short-circuit member.