This work treats the thermotropic structural change of the disialoganglioside (G(D1)) micelles studied by using synchrotron radiation X-ray scattering. Scattering data and analyses show that thermotropic structural change around 20 degrees C accompanies the contraction of the whole micellar dimension and the internal structural change of the micelles. Double-shell modeling analyses reasonably describe the observed changes in the experimental scattering curves, distance distribution functions, and structural parameters, The modeling analyses show that the major changes of the micellar structure induced by the elevation of temperature are the contraction of the hydrophilic region and the increase of the average scattering density, suggesting the change of the oligosaccharide chain conformation from an extended one to a folded one. Simultaneously, the minor extension of the hydrophobic region occurs with a slight increase of the average scattering density, suggesting a minor rearrangement of the hydrocarbon chains. We assume that such a thermotropic structural change around room temperature will be a typical characteristic of glycolipids containing long oligosaccharide chains with sialic acid residues in hydrophilic heads, which would affect stability of membrane structure and relate to promotion of various physiological surface events in biomembranes.