To provide a method and device for decomposing pollutants such as PCB, furan, dioxins highly toxic and hard to dispose and making them non- noxious by irradiating infrared laser beams.

Pulluranis similar to PCB, furan and dioxins are detected by using a portable FTIR device or a portable spectrophotometer and also their resonance absorption conditions are detected. Next, based on the detected resonance absorption conditions, an infrared laser beam having a wavelength with which the detected pollutants can be selectively decomposed is selected. Then, the selected infrared laser beam is irradiated to the pollutants in the air, in the soil, or in water, or the like, and the pollutants are thermally decomposed by selectively exiting them. Finally, by measuring the absorption and radiation spectra of the pollutants and their decomposed products or by-products by using the portable FTIR device or portable spectrophotometer, the presence of the remaining pollutants, decomposed products and by-products is confirmed.