A new stilbene glycoside (I), mp 258°, [α] D-86.0°, C27H26O12·1/2H2O, together with 3, 5, 4'-trihydroxystilbene 4'-O-β-D-glucopyranoside (II) and d-catechin (III), was isolated from the Japanese rhubarb, "Shinshu Daio", and the structure of I was established to be 3, 5, 4'-trihydroxystilbene 4'-O-β-D-(6''-O-galloyl)-glucopyranoside on the bases of chemical and spectral evidence. The occurrences of the stilbene glycosides (I, II) and III in commercial Chinese rhubarbs were examined by thin-layer chromatography, which revealed that almost all kinds of rhubarbs contained II and III while I appeared in the limited ones.