PURPOSE: To increase a photoelectric conversion output over the entire range of in-use wavelength by adjusting the quantity of light incident from a light dispersing element to an image sensor by using a light-intensity adjustment member.

CONSTITUTION: Light from a light source lamp 3 is guided to a light dispersing element 7 by a concave mirror 6 to disperse the light there, and the resulting light is condensed through a condenser lens 11 to irradiate a linear image sensor 12 with the condensed light. The image sensor 12 performs a self-scan from one terminal bit to the othe terminal bit synchronizing with clock pulses supplied to a driving circuit 13 to output photometric data, which is passed through a signal processing circuit 14 and an amplifier, thereby outputting a photoelectric conversion signal. A light-intensity adjustment member 10 is provided in an optical path between the light dispersing element 7 and image sensor 12 of the spectrometry device like this. When the member 10 is of a filter type, the light transmittivity of the filter is given light and shade, and consequently the photoelectric conversion output is increased over the entire range of in-use wavelength.