Abstract: A process for purifying inert gas removing impurities such as oxygen, carbon dioxide and moisture that are contained in inert gas each in a slight amount with the use of reproducible purification agent comprises: manganese oxide (1), and at least one kind of metal oxide (2) selected from vanadium oxide, chromium oxide, iron oxide, tin oxide, zirconium oxide, bismuth oxide, niobium oxide and tantalum oxide as effective component; and preferably further contacting with a synthetic zeolite. The process enables to prevent degradation of the removing capability for impurities even after many returns of reproduction of the purification agent, and to continuously feed highly pure inert gas.