PURPOSE: To enable accurate fetching of the output signal for angular velocity detection, by directly assembling the diode generating microwaves in a wave guide in a closed looped shape and thus stabilizing the generation of the microwave.

CONSTITUTION: Microwaves generated from a diode 2, upon receiving an electric voltage from a stabilized power source 3, rotate in a wave guide 1 in the mutually opposite directions. These microwaves are provided with oscillating frequencies f1, f2 and mixed for detection after entering into a mixing detector 4 through a slit 16. When the microwave portion is in the absolutely still condition, both frequencies assume the same value producing a zero output from the detector 4 allowing a frequency display 7 to indicate zero. When the microwave portion is rotating with respect to the absolute spoce, a difference is produced between both frequencies f1, f2 and upon mixing for detection, a low frequency signal of Δf is generated. By assembling directly the diode 2 in the wave guide 1, the microwave can be generated in a stable way with the oscillating condition only of a ring length of the wave guide 1 and thus, an output of the frequency difference can be fetched out with high accuracy.