PURPOSE: To rapidly obtain the subject high-quality pulp in high yield under ordinary pressure by primarily digesting a nonwood cellulosic raw material with a digesting chemical containing water, hydrogen peroxides, a caustic alkali and hydrogen peroxide stabilizer, etc., at a high speed under specific conditions in one stage and then removing impurities.

CONSTITUTION: A digesting chemical of a mixture consisting of water, hydrogen peroxide or hydrogen peroxide generator, a caustic alkali and hydrogen peroxide stabilizer or anthraquinones added thereto and a nonwood cellulosic raw material as a pulp raw material are fed to a digester so as to provide 2-15l/kg liquid ratio and forcibly stirred, mixed and digested at a temperature below the boiling point under ordinary pressure at a high speed in one stage. A refined pulp is obtained simply by removing impurities, such as residue or dust, from the formed digested materials without grinding, beating and macerating. Thereby, unbleached pulp of high whiteness degree is produced from the nonwood cellulosic raw material.