Method for producing 5-hydroxymethylfurfural using cellulose as raw material

The purpose of the present invention is to provide: a method for producing 5-hydroxymethylfurfural (5-HMF) from a biomass with high yield while preventing the production of any by-product; and an apparatus which can be used for the method. The present invention relates to a method for synthesizing 5-hydroxymethylfurfural continuously using a cellulose as a raw material, said method comprising the steps of: mixing the cellulose with supercritical water or subcritical water to hydrolyze the cellulose; cooling the resultant reaction solution and then reducing the pressure of the reaction solution to adjust the temperature and the pressure of the reaction solution to a temperature and a pressure both suitable for the dehydration reaction of a monosaccharide; and mixing an acid, which has been heated to a temperature that is up to 100˚C above or below the dehydration reaction temperature for the monosaccharide, with the reaction solution and then carrying out the dehydration reaction of the monosaccharide to produce 5-hydroxymethylfurfural.