The solid state laser comprises the laser medium 11 for absorbing the pumping light 12 from the LD 10 and generating or amplifying the light having a predetermined wavelength and a heat sink comprising the first block 15a, the second block 15b and the third block 15c for aligning the laser medium 11, cooling the laser medium 11 and reflecting the pumping light 12. The laser medium 11 has an arcuate light incident surface A and a flat reflection portion. The pumping light 12 having a diffusing angle is converted into parallel light by the light incident surface A, thereby pumping the laser medium 11 uniformly. The flat reflection portion makes it easy to align laser medium 11 having anisotropic characteristic and helps to efficiently pump the laser medium 11 by reflecting the reflection light substantially in parallel with the incident light.