PURPOSE: To secure adjustment for the power distribution ratio of the output waveguide provided by branching with a simple method by installing the impedance matching circuit to the input waveguide at the position deviated from the center line of the input waveguide.

CONSTITUTION: Output waveguide 2 is connected to one H face of input waveguide 1 featuring a rectangular cross section, and output waveguide 3 is connected to the other H face each. The same measurement is secured for the rectangular cross section between waveguide 2 and 3, thus forming a T-type waveguide branching unit. Conductor bar 4 is inserted to the position deviated from center line 5 for waveguide 1 of the T-type waveguide branching unit in order to adjust the distribution ratio of the magnetic force line to waveguide 2 and 3. Thus an adjustment is given to the ratio of the power to be supplied to waveguide 2 and 3, and at the same time an impedance matching circuit is formed to waveguide 1. This matching circuit consists of conductor bar 4 the both ends of which are connected to both faces E of waveguide 1.