To provide a system of a Q-switch type pulse laser beam for forming a mark on a part of a gemstone with an accurate positioning.

The system includes a semiconductor-excited Q-switch type solid state laser beam energy source 1, a gemstone fitting system which realizes an optical access to a fitted work 11, an optical system which converges the laser beam energy supplied from the laser beam energy source upon a cut gemstone, a movable stage provided with a control unit and for moving the gemstone fitting system relative to the optical system so that the converged laser beam energy is supplied to a predetermined position on the gemstone, an imaging system for observing the gemstone from plural advantage points, and a rigid frame which supports the laser beam energy source, the optical system, and the stage in a fixed relative positions, and has a resistance against the different movements of the optical system and the stage so that the elimination of the error in positioning due to vibration is enhanced.