To solve problems: pulps having fibers longer than the fibers of wood pulps can be produced from various hemps, and also from raw materials comprising leaves of pineapple, banana or the like, and they are valued highly as long fiber pulp; however hemps, etc., are short in resource, and the leaves of banana and pineapple are generated in a large quantity, but most parts of them are wasted and not used since they contain a large amount of water and non-fibrous materials besides the long fiber, and they are heavy and apt to rot, difficult in transportation and storage, hard in usage, difficult in pulp production when used as they are, large in a chemical consumption rate, and so on.

It becomes possible that a large amount of raw materials are treated with saved labor for decomposing and solving out non-fibrous materials by cutting leaves and sheathes of long fiber-containing plants into adequate lengths, crushing cells and subjecting them to a biotreatment with bran malts. This enables continuous cooking of long-fiber raw materials, and a method for manufacturing pulp in high yield with little chemical consumption rate in cooking is achieved.