To provide a gas treating apparatus for purging harmful materials in a waste gas efficiently by plasma discharge without causing the lowering of energy efficiency, the increase of the size of the whole apparatus and the complication of its constitution.

This gas treating apparatus has a creeping discharge type plasma discharger 10 constructed by forming at least a discharge surface 11F in a discharge tube 11 from an adsorbing material provided with an action to adsorb NO (harmful material) to be purged and is constituted so that NO (harmful material) in the waste gas from a diesel engine which is a gas producing source is adsorbed to be captured on the discharge surface 11F of the discharge tube (discharge body) 11 and the captured NO is purged by the plasma discharge produced on the discharge surface 11F.