The present invention has the object to dehydrate hydrous matters without denaturing or deteriorating them by using a dehydrating agent comprising an anhydrous cyclotetrasaccharide, and provides a dehydrating agent comprising the cyclotetrasaccharide; a method for dehydrating hydrous matters through a step of incorporating, contacting or coexisting the cyclotetrasaccharide into, with, or in the hydrous matters; and dehydrated products obtainable thereby.