refer to fig4 and obtains the measurement values amount of light f 0 through f 4 in the example of fig1 each calibration sample is measured once since the measurement number of each calibration sample is 1 note that each calibration sample also may be measured several times for example three times to improve the accuracy of the obtained calibration in such case the measurement value of each calibration sample is the average value of several measurement values obtained by a plurality of measurements in step s 602 the controller 200 of the measurement section 2 prepares a diluted calibration sample of user specified calibration sample cx x is selected from 0 through 4 which contains known concentration referred as mx the user specified calibration sample cx is diluted 40 times measurements according to steps s 501 through s 506 and steps s 404 through s 415 refer to fig5 are performed and the measurement value fx u2032 is obtained and stored in memory since c 4 is selected as the calibration sample to be used for diluting measurement in the example of fig1 a diluted calibration sample is prepared by diluting c 4 by 40 times and measurement is performed on it although steps s 601 and s 602 are listed as separate steps in the drawing in.