PURPOSE: To enable frequent execution of base line correction measurement and also to increase the efficiency of sensing of a light transmitted through a sample, to improve an S/N ratio in measurement and thereby to improve the precision in measurement in the case when spectral measurement is conducted while the sample is made to flow through continuously.

CONSTITUTION: A spectrochemical analyzer is so constructed that a light diffracted spectrally by a spectrometer 5 is transmitted through a flow cell 2 and a dummy cell 3 by using two optical fiber bundles 6 and 7 and lights transmitted therethrough are detected by the same detector alternately by using a shutter 8 or the like. The two optical fiber bundles 6 and 7 are so constructed that the diameters of the optical fiber bundles on the light-sensing side are larger than those of the optical fiber bundles on the light-projecting side, and the two optical fiber bundles 6 and 7 are held in the same protective tube 12.