PURPOSE: To reduce a reflection factor very much by providing a step on the inside wall face of a waveguide in a specific position from the front end of a microwave absorber in the direction of microwave incidence.

CONSTITUTION: A step 5 is provided in the center part on the inside wall face in the longer side direction of a rectangular waveguide 1 and a half of this inside wall face is higher by one step. A wedge-shaped microwave absorber 3 is fixed to this inside wall face of the waveguide higher by one step by soldering, an adhesive, or the like, and its front end does not form an acute angle but has about 0.5mm thickness. A length L between the edge of the step 5 and the front end of the wedge-shaped microwave absorber 3 is set to be equal to λ9/4 (Aλ9 is the guide wavelength) within the range of L=0∼2a where (a) is the length in the transverse direction of the inside of the waveguide. Thus, reflected waves generated in two positions, namely, the step 5 and the front end part of the wedge-shaped microwave absorber 3 act so that they are cancelled by each other, and the reflected wave in a microwave terminator is practically reduced very much.