To facilitate manufacture and adjustment, and to fix and hold an adjusting state.

A casing 5 is constituted of an upper casing 5a and a lower casing 5b, which are divided into two at the center of a face H in a waveguide 3. V-shaped storage grooves 9a and 9b storing adjusting screws 8 are installed in the casings 5a and 5. A recessed groove 5bc is installed at a lower part of one storage groove 9b and a flat spring 10 is installed. The casings 5a and 5b are jointed in a state where the adjusting screws 8 are stored in the storage grooves 9a and 9b so as to assemble the casing. The flat spring 10 presses the adjusting screw 8 in a direction of the other storage groove 9a in an assembled state, the adjusting spring 8 is prevented from being loosened and an adjusting state can be kept.