PURPOSE: To produce maltose and maltotriose by allowing an enzyme originating from a variant of Clostridium to act on starch powder or starch hydrolyzate at a temperature of ≥60°C and a pH of 4-6.5.

CONSTITUTION: An enzyme is prepared that originates from a variant of Clostridium and has α-amylase activity-having group and pullulanase activity- having group in the same protein molecule where these active groups hydrolyze starch to maltose and maltotriose. This enzyme and starch or starch hydrolyzate are allowed to react with each other at ≥60°C and a pH of 4-6.5 to form maltose and maltotriose. This enzyme has a relative molecular mass of 185000±35000 in the presence of sodium dodecylsulfate determined by the polyacrylamide gradient gel electrophoresis.