The invention discloses a Balun applicable to a dipole antenna. The Balun comprises a first part arranged on the front side of a substrate and a second part arranged on the back side of the substrate respectively; the first part of the Balun comprises a first horizontal part and four juxtaposed vertical parts, wherein one end of each vertical part is connected to the first horizontal part; two vertical parts located at the outer side are C microstrip lines, two vertical parts located in the middle are B microstrip lines, the other ends of the two vertical parts are connected to a second horizontal part, a window area surrounded by the two vertical parts, the first horizontal part and the second horizontal part is provided with an A microstrip line, and the relative outer side of the first horizontal part and the second horizontal part is provided with a first inputting end and a first outputting end respectively; the second part of the Balun comprises two port lines, the outer end of the two port lines are adopted as a second inputting end and a second outputting end respectively, the inner ends of the two port lines extend to a projection area of the window area on the back side of the substrate respectively, and communicated with the A microstrip line in a conductive mode through a via hole.