A multi bandwidth balun is provided, including a main signal port, a main inductor electrically connected to the main signal port, a first inductor inducted mutually with the main inductor to constitute a first inductor of a first conversion circuit, a first capacitor module connected in parallel to the first conversion circuit, two first signal ports electrically connected to the first capacitor module, a first main capacitor electrically connected to the first signal port and the first capacitor module therebetween, a second inductor inducted mutually with the main inductor to constitute a second inductor of a second conversion circuit, a second capacitor module connected in parallel to the second conversion circuit, two second signal ports electrically connected to the second capacitor module, and a second main capacitor electrically connected to the second signal port and the second capacitor module therebetween.