We here report a continuous method in which glucose is converted by reaction with supercritical water at 400 degrees C and 30 MPa, to erythrose in as high as 50 wt %. This method is noncatalytic and operates continuously with a reaction residence time of as low as 0.11 s. Erythrose is stable under these conditions and its selectivity changes only slightly from about 50 to 45 wt % over the range of glucose conversion from 50 to 90 wt %. This method has an advantage over other conventional methods in that it is rapid and continuous and results in comparative high yields of erythrose. Furthermore, the use of toxic chemicals is reduced and product separation is facilitated.