When a wavelength of an electromagnetic wave in an electromagnetic wave propagation space (4) is λ, and n is an integer, in a case where a first conductive layer (2) and a second conductive layer (3) are short-circuited in a first end surface (7b), the more distant an electromagnetic wave output interface (6) is from an electromagnetic wave input interface (5), the closer to a distance of λ/4+n·λ/2 from the first end surface (7b) which is short-circuited the electromagnetic wave output interface is installed, and, in a case where the first conductive layer (2) and the second conductive layer (3) are not short-circuited in the first end surface (7b), the more distant the electromagnetic wave output interface (6) is from the electromagnetic wave input interface (5), the closer to a distance of n·λ/2 from the first end surface (7b) which is not short-circuited the electromagnetic wave output interface is installed.