To provide an oxide excellent in thermal stability and catalytic service life, and to provide a method for producing the oxide and a method for producing chlorine stably over a long period of time in the presence of the oxide.

The oxide is produced by depositing phosphorus oxide and ruthenium oxide on a carrier consisting of at least one compound selected from the group consisting of titania, alumina, silica and zirconia. It is preferable that a phosphorus compound is deposited on the carrier, the phosphorus compound-deposited carrier is fired in an oxidizing gas atmosphere to obtain the phosphorus oxide-deposited carrier, a ruthenium compound is deposited on the phosphorus oxide-deposited carrier, and the ruthenium compound-deposited carrier is fired in the oxidizing gas atmosphere to produce the oxide. Chlorine is produced by oxidizing hydrogen chloride by oxygen in the presence of the oxide.