Abstract: Novel trehalase having the properties that it hydrolyzes .alpha.,.alpha.'-trehalose, 2,2'-dideoxy-.alpha.,.alpha.'-trehalose and 2-deoxy-.alpha.,.alpha.'-trehalose into the respective constituting sugars while it does not act on neotrehalose, lactose, maltose, celobiose and sucrose; its optimum pH is 5 to 6; its optimum temperature is 65.degree. C.; it is stable against heating up to 65.degree. C.; its molecular weight as measured by a gel filtration is 400,000 to 500,000 while the molecular weight of the subunit as measured by a sodium dodecylsulfate--polyacrylamide gel electrophoresis is 180,000 to 250,000; its isoelectric point as measured by an isoelectricfocusing is 2.7; and it is a glycoprotein.