PURPOSE: To obtain a ring laser gyro having a long life and high reliability by sealing a gyro body and a mirror with a sealing member made of a low melting point active alloy.

CONSTITUTION: A gyro body 1 formed with a closed laser optical path 1 along the peripheral edge of a square-shaped block made of glass is formed at the periphery of the block, and a cathode 3 and anodes 4a, 4b are attached to the periphery of the body 2 to oscillate a laser light in the path 1. Pairs of high reflecting side mirrors 5, 5 and output side mirrors 6, 6 are sealed with a sealing member 20 made of low melting point active alloy at the corners of the body 2. The alloy contains as main ingredients low melting point solder alloy made of two types of elements selected from Pb, Sn, Zn, Cd, Bi and element Sb. Thus, it can prevent it from leaking from a sealed section and reduce gas exhaust from the alloy.