A cleaning process of exhaust gas which includes the steps of bringing the exhaust gas containing at least one of nitrogen oxides or organic solvent into contact with a cleaning agent including metal as a reductive cleaning agent component and metal oxide as an oxidative cleaning agent component or including lower valent metal oxide as a reductive cleaning agent component and higher valent metal oxide as an oxidative cleaning agent component while heating them. A cleaning process of exhaust gas containing nitrogen oxides and/or organic solvent with high and varying concentration discharged from a manufacturing process of semiconductor capable of easily cleaning at relatively low temperature and with high decomposition factor without using large-scale cleaning apparatus or a complicated structural cleaning apparatus is provided.