PURPOSE: To easily know the change of data with time by increasing or decreasing the data by a data number increasing and decreasing means, reading the spectrometry data corresponding to the data number after the change out of a spectrometry data memory means and graphically displaying the same.

CONSTITUTION: The spectrometry data which are measured are stored as the data of the data number 1Wn into the memory means MEM. The data number increasing and decreasing means NUM increases or decreases the data number of the spectrometry data to be read out of the memory means MEM. The spectrometry data with the data number after the change is read out of the memory means MEM and is displayed on a display means DSP when the data number changes. The spectrometry values with respective wavelengths are graphically displayed on the display means DSP.