The X-ray diffraction of adsorbed water molecules in a slit-shaped carbon nanospace of width 1.4 nm was measured at 303 K. The electron radial distribution function of the adsorbed water showed that the number of nearest-neighbor molecules of the adsorbed Water is less than that of bulk liquid water and that the adsorbed water has a long-range ordered structure compared with bulk liquid water. The results indicate directly:the formation of an ordered assembly structure of water adsorbed in the hydrophobic nanospace.