A noise filter can reliably reject an in-phase component included in a differential signal without generating anti-resonance at a target frequency reject and, a transmission device including such a noise filter.Ends of a pair of coils are connected to a pair of transmission lines in the vicinity of the transmitting circuit, and other ends are short-circuited. The coils are magnetically coupled so that the magnetic flux is cancelled regarding the in-phase component that transmits the pair of transmission lines, and the magnetic flux is increased regarding an opposite-phase component that transmits the pair of transmission lines. A series circuit, which includes an inductor and a capacitor connected in series, is connected to the pair of coils and ground. Each value of the pair of coils, the inductor, and the capacitor is set so that a resonance frequency of the in-phase component is a target frequency.