The invention provides a waveguide device based on a metamaterial. The waveguide device comprises a waveguide tube and a separating piece arranged in the waveguide tube for separating the internal space of the waveguide tube into two segments. The separating piece is made of the metamaterial, and the impedance of the metamaterial is equal to or close to the impedance of the air, and therefore, when an electromagnetic wave enters the separating piece of the metamaterial from the air, the reflection is low, the transmission is high, the interference to an incoming wave is reduced, and an emission source can not be damaged due to the reflection.