A non-dispersion type infrared analyzer for simultaneously determining plural components of a sample fluid, wherein a standard fluid and a sample fluid are alternately supplied in a cell and a plurality of pneumatic detectors, each of which corresponds respectively to one component to be determined, are arranged optically in series with respect to a light source. The extremely troublesome zero-adjustment, adjustment of the phases and re-adjustment of the compensation for eliminating the influences of interference components due to changes in the zero-drift or the deviation of phases are not required.