A dual band balun filter that includes a first coupled-line section pair provided with a first terminal; a second coupled-line section pair configured to be connected to the first coupled-line section pair, a third coupled-line section pair, and a fourth coupled-line section pair, respectively, and the fourth coupled-line section pair is provided with a second terminal; the third coupled-line section pair is provided with a transmission line and is connected to a fifth coupled-line section pair that is provided with a third terminal; and each of the first to fifth coupled-line section pairs is formed with partial coupled stepped impedance resonators (SIRs).