It is intended to provide a method for producing a material which contains a xylooligosaccharide rich in xylobiose and xylotriose, an antioxidant active substance and dietary fiber and is useful as a food material or health supplement by a simple process efficiently at a low cost. A hemicellulose-containing plant resource such as bagasse is subjected to a steam blasting treatment (2.5 Mpa, 70 seconds) and wheat bran is mixed with this steam blasting-treated substance. After the water content of this mixture is adjusted to about 50%, koji is prepared with Aspergillus oryzae with a high xylanase activity obtained by single spore isolation from Aspergillus soya (NFRI1147). Water is added to the resulting koji and the steam blasting-treated substance is mixed with a koji dispersion in which the koji is dispersed in water and after the water content of this mixture is adjusted to about 50%, fermentation is carried out. A fermentation termination treatment is carried out after the fermentation and fine grinding is carried out after drying. As the steam blasting-treated substance to be mixed with the koji dispersion, an amount 8 to 10 times the steam blasting-treated substance used for the koji preparation is used.Linvention est prévue pour fournir un procédé de production dun matériau qui contient un xylooligosaccharide riche en xylobiose et en xylotriose, une substance active antioxydante et une fibre diététique et est utile en tant qualiment ou complément diététique au moyen dun procédé simple et efficace à faible coût. Une ressource végétale contenant de lhémicellulose telle que la bagasse est soumise à un traitement de nettoyage à la vapeur (2,5 MPa, 70 secondes) et du son de blé est mélangé à cette substance traitée par un nettoyage à la vapeur. Après que la teneur en eau de ce mélange ait été ajustée à environ 50 %, le koji est préparé avec lAspergillus orizae ayant une activité élevée de xylanase que lon obtient par isolement dun seul spore de lAspergillus soya (NF
