To provide a method for producing an olefin oxide by reacting an olefin with oxygen substantially without using hydrogen.

The method for producing the olefin oxide includes a step of reacting the olefin with oxygen in the presence of a catalyst containing silver, titanium and a lanthanoid element. The catalyst is preferably obtained by a preparation method including a step of obtaining a first complex from a compound containing the lanthanoid element and a titanium compound, a step of obtaining a second complex by heat-treating the first complex, and a step of mixing the second complex with at least one selected from the group consisting of metal silver and a silver compound.