To provide a method capable of producing an oxide (oxidation product) in a high selectivity in a high yield.

An oxide is produced by a reaction process for oxidizing a substrate in the presence of an oxidizing agent (an alkali metal bromate, etc.), represented by the formula M(XOm)n (M is a hydrogen atom or a metal; X is a halogen atom; m is an integer of 1-4; n is an integer of 1-3) and a termination process for adding a reducing agent (a sulfite, a thiosulfate, a pyrosulfate, etc.), to the reaction mixture and deactivating an oxidation activity species in the reaction mixture. The addition of the reducing agent may be carried out after the conversion of the substrate into the oxide reaches ≥80 mol% and before the ratio of the decomposition product of the oxide to the oxide exceeds 10 mol%. In the reaction process, both the oxidizing agent and an activator which acts on the oxidizing agent and generates a halogen molecule being an oxidation activity species may be used.