To provide a method for cleaning exhaust gas by which nitrogen oxides (NOx) in exhaust gas discharged from an exhaust gas generation source, where the NOx concentration is fluctuated suddenly in a short time, can be deoxidized/removed and an added deoxidizer can be prevented from being discharged in an unreacted state.

In this method for removing NOx in the exhaust gas discharged from the exhaust gas generation source where the NOx concentration in the exhaust gas is fluctuated violently, the exhaust gas is brought into contact with a protonic β-zeolite catalyst in the presence of methanol and/or dimethyl ether to deoxidize/remove NOx, and succeedingly the NOx-removed exhaust gas is brought into contact with an oxidation catalyst to oxidize/remove the unreacted deoxidizer.