PURPOSE: To attain easy and effective synthesization of electric powers with a compact synthesizer by securing such a constitution where the electric powers delivered from plural high frequency electric power sources are synthesized by a dielectric resonator and taken out to outside through a transmission line.

CONSTITUTION: A 1st oscillation circuit consists of a 1st Gunn diode 26a, a 1st strip line 22a and a dielectric resonator 24. While a 2nd oscillation circuit consists of the a Gunn diode 26b, a 2nd strip line 22b and the resonator 24. Then both oscillation circuits are magnetically connected to each other by the resonator 24. When the DC voltage +VB is impressed to a bias terminal, the voltage +VB is applied to both diodes 26a and 26b and the microwave electric powers are delivered from both oscillation circuits. In this case, those outputs are extracted with the same frequency and same phase out of a coaxial connector 38 in a synthesized form. Thus the electric powers of high frequency power sources are easily and effectively synthesized.