PURPOSE: To improve measurement sensitivity by using sapphire added with titanium as a wavelength variable solid-state laser so that the disturbance by fluorescence is averted.

CONSTITUTION: The Raman detector is constituted of a titanium sapphire laser oscillator 1, a half mirror 2, a sample cell 3, a polarizer 4, a polarization eliminating plate lens 5, a condenser lens 6, a spectroscope 7, and a detector 8. The so-called titanium sapphire laser in which the laser medium is the sapphire added with the titanium is used as the wavelength variable solid-state laser for the light source of a stimulating laser beam, by which the Raman spectra of the sample to be measured are selectively and easily measured in the stable state.