PURPOSE: To obtain a solid laser device which does not generate any temperature distribution in a solid laser medium even if a temperature difference is produced in a refrigerant by reducing the channel sectional area of a region cooling the solid laser medium at a downstream side as compared with that at an upstream side.

CONSTITUTION: A surface of transparent screening plates 140a and 140b opposing lamps 12a and 12b is nearly in parallel with the surface of a YAG slab laser medium 11 and that opposing the surface of a medium 11 is inclined so that the thickness is increased from an upstream side toward a downstream side. Then, the channel sectional area of a region cooling the medium 11 of a refrigerant circulation path 16 is reduced at the downstream side and a cooling water is delivered from a refrigerant delivery port 160b through a channel which is formed by the rear and front surfaces of the medium 11 and the transparent screening plates 140a and 140b. Therefore, when the ratio of sectional area between the upstream and downstream sides is set properly, the amount of cooling can be made equal at the upstream and downstream sides, thus cooling the solid laser medium without generating a non-uniform temperature distribution.