improved by substantially 15 in comparison with that of a composite laser rod in which the non doped portions are not disposed at both ends in the next place with reference to fig1 a composite laser rod 80 different from ones described above will be explained as a laser rod a single crystal yag laser rod 81 that has a diameter of 2 mm and a length of 30 mm and contains 0 8 atomic of nd is prepared as a non doped ceramic pipe in the periphery thereof one that is prepared with slurry of y 2 o 3 is prepared in a pre baked y 2 o 3 ceramic pipe the single crystal yag laser rod 81 is inserted followed by baking at 1700 degree centigrade for 10 hour and furthermore followed by processing and thereby the composite laser rod 80 that has a diameter of 3 mm and a length of 30 mm and in which to the periphery of the single crystal yag laser rod 81 the ceramic y 2 o 3 pipe 82 is bonded is prepared the rod is oscillated with the resonator similar to one described in fig3 and the thermal lens effect is compared with that of one in which a ceramic yag pipe is bonded to a periphery since the thermal conductivity of the y 2 o 3 pipe is such large as twice.