Abstract: An IR-spectrometric analyzing procedure, the measuring absorbance and reference absorbance being detected simultaneously from an IR light beam conducted to pass through the sample and diffracted to a spectrum. An IR spectrometer comprising a light source (1), a sample cuvette (5), a diffraction member (6), detectors (7) and a calculating means (9) for determining the content values of the sample corresponding to the measuring absorbance, the detectors (7) having been arranged to detect the measuring absorbance and the reference absorbance simultaneously from the beam that has passed through the sample and been diffracted to a spectrum.