Abstract: There is provided a nitrogen compound analyzer capable of easily and accurately measuring the two components NH3 and NO2 or each nitrogen compound component in a single sample. The nitrogen compound analyzer includes: a plurality of sample treatment systems by which a single sample is divided and which includes (A) a treatment system having oxidation means for oxidizing ammonia in the sample and conversion means for converting nitrogen dioxide in the sample to nitrogen monoxide, (B) a treatment system having conversion means for converting nitrogen dioxide in the sample to nitrogen monoxide, and (C) a treatment system in which no conversion treatment is performed on a specific component in the sample; changeover means capable of providing a specific combination of any of the treatment systems (A), (B) and (C); and at least one measurement means for continuously measuring nitrogen monoxide in the sample.