A waveguide and an attenuation pole waveguide bandpass filter with a simple structure without any additional structure such as a negative cross coupling between resonators.The attenuation pole waveguide bandpass filter arranged at right angle to the longitudinal direction (radio wave propagation direction) is composed only of conductors. The conductor comprises depressions each opening outwardly and having a non-conducting region which continues from the inside of the opening section to the outside, and a window in the conductor section between these opposed depressions. In an alternative embodiment, such conductor shall be covered by a dielectric such as a resin.