PURPOSE: To maintain the temperature of a laser medium to be low and to improve Raman conversion efficiency in Raman laser for performing wavelength conversion of a laser beam between a pair of mirrors to a longer wavelength side with the rotation scattering transition of a gas molecule by multiple reflection.

CONSTITUTION: Since a main body container 35 preserving a laser medium gas is formed in a hand drum shape, where the diameter at the center is long and that at both edges is short. for the shape of multiple reflection of a laser beam, the distance between the outermost shell part of a laser beam multiple reflection part 24 and a main body can be extremely reduced especially at the center part, thus enabling the heat of the laser medium gas to be transferred to the main body efficiently.