an analyzing apparatus provided with a spectroscopic photometer , in which light emitted by a deuterium lamp enters a flow cell ; light transmitted by the flow cell is divided into two light beams by means of a beam splitter , one of which is received by a detecting element for sample measurement and the other of which is received by a detecting element for monitoring through a filter transmitting only light in a predetermined wavelength region , which is not essentially absorbed by the sample ; and a signal processing device compares the output signal of the detecting element for sample measurement with that of the detecting element for monitoring and effects necessary operations .