The quantitative analysis by near infrared spectroscopy is being used for many applications in the life infrastructure fields related to environment because of its non-destructive and rapid features in the measurement. Accuracy of the quantitative analysis by near infrared spectroscopy depends on the performance of the near infrared spectrometer. The reason is that the changes of the near infrared spectral waveform caused by the quantity of the constituents are really subtle. Design concept for NIR spectrometers for a special purpose is explained.