A semiconductor ring laser gyro comprises: a semiconductor laser for emitting light from each of both ends thereof; a splitting means for splitting and guiding the light emitted from the semiconductor laser into two axis directions; a plurality of reflecting means for reflecting the light split and guided by the splitting means into the two axis directions; two optical circuits, in each of which the plurality of reflecting means cause the light to travel in a plane and to enter an end of the semiconductor laser opposite to the end from which the light is emitted; and a blocking means for blocking light traveling in one of the two optical circuits.