PURPOSE: To enable measurement of specimen light in high sensitivity and to measure the intensity of each wavelength of said specimen light at a high speed, by inputting the operation signal of a variable interference filter and the output voltage of a photomultipilier to a recording apparatus.

CONSTITUTION: The pulse signal (b) outputted from a pulse motor controller 21 is inputted to a linear motor to operate the variable interference filter 9 above said motor 5. Specimen light to be analyzed is permeated through the variable interference filter 9 while condensed onto said filter 9 from a pervious orifice 3 through a condensing lens system and the obtained parallel light is inputted to a photomultiplier 18 through the filter and a shutter 17 opened only during measurement and the output signal (a) is inputted to a memoryscope 20 as vertical voltage. On the other hand, the pulse signal (b) is inputted to a counter 22 to be converted to a signal b1 which is, in turn, inputted to the memoryscope as vertical trigger voltage. Therefore, the wavelength characteristic curve of specimen light is displayed by the memoryscope 20.