In a method for producing a hydrolysate in which an organic compound and water are mixed and a hydrolysis reaction of the organic compound is performed, shear flow of the organic compound and the water at a shear rate U/Dmin of 5.5 sec.sup.-1 or more (where Dmin is a flow channel minimum inner diameter (mm) in a mixing section and U is a flow rate (mm/sec) of a mixture of the organic compound and the water in the mixing section), thereby mixing the organic compound and the water, and the hydrolysis reaction of the organic compound is performed at a reaction temperature of 150.degree. C. to 350.degree. C. and a reaction pressure equal to or higher than a saturation vapor pressure of the water.