Methods of obtaining an olefin oxide compound from an olefin type compound and a hydroperoxide in the presence of a catalyst, are publicly known. As a catalyst used herein, specified titanium-containing silicon oxide catalysts are disclosed in, for example, patent literatures (e.g. U.S. Pat. Nos. 4,367,342 and 5,783,167, JP-A-7-300312, JP-A-2000-107604, JP-A-2000-107605, JP-A-2000-109469, JP-A-2000-109470, JP-A-2000-117101, JP-A-2000-119266, JP-A-2001-286768, JP-A-2002-224563, JP-A-2002-239381, JP-A-2004-195379 and JP-C-2909911). As these catalysts are used as a fixed bed catalyst, the catalysts in a large amount are filled in a reactor every several months to every several years. As the result, these catalysts are often successively produced and probably stored for long period. However, findings regarding suitable conditions under which the catalysts are stored for long time, have never been shown.