incorporating into the light receiver 14 and may prevent the light sensor 14 from being saturated however when the transmittance of the light penetrating the optical filter 13 is decreased namely when the shielding effect of the optical filter 13 is increased the transmittance of the raman scattering light is also decreased practically the minimum value of the transmittance of the light penetrating the optical filter 13 is approximately 10 u2212 8 namely all the first reflected stray light 61 is not shielded and some of the first reflected stray light 61 penetrates the optical filter 13 the some of the first reflected stray light 61 incorporates into the light receiver 14 and lowers the measurement accuracy of the concentration of the biogenic substance furthermore living bodies have substances having a raman spectrum which overlaps the raman spectrum of the biogenic substance such as glucose even if the optical filter 13 is used the raman scattering light hereinafter u201c the interruption raman light u201d generated by the substances fails to be decreased this also lowers the measurement accuracy of the concentration of the biogenic substance in order to solve the above mentioned problem the steps d to f are performed in this embodiment of the present invention it is preferred that the step d and the step e are performed at the same time it is more preferred that the steps d to f are performed at the.