PROBLEM TO BE SOLVED: To provide a gas cleaning method and device by which the appropriate clean air is rapidly obtained in accordance with the degree of contamination in the space where there are human beings, animals, plants, foods, etc. SOLUTION: A photoelectron from a photoelectron emitting material 5 is used to clean a gas in this gas cleaning device. A fan 8 operated in accordance with the degree of contamination of a gas to be treated is set in a passage connected to a gas cleaning part. A reticular or fibrous material is preferably used as the photoelectron emitting material 5. One or more kinds between the cleaning part using a photocatalyst or an ion-exchange fiber and a negative ion generating part can be jointly equipped in the cleaning part.