  We report on a wide-area (48' x 9') imaging survey of faint galaxies in R and
I bands toward the 1338+27 field where an unusual concentration of five QSOs at
z\sim1.1, embedded in a larger-scale clustering of 23 QSOs, is known to exist.
Using a quite homogeneous galaxy catalog with a detection completeness limit of
I~23.5, we detect a significant clustering signature of faint red galaxies with
I > 21 and R-I > 1.2 over a scale extending to ~20h^{-1}_{50} Mpc. Close
examination of the color-magnitude diagram, the luminosity function, and the
angular correlation function indeed suggests that those galaxies are located at
z~1.1 and trace the underlying large-scale structure at that epoch, together
with the group of 5 QSOs. Since the whole extent of the cluster of 23 QSOs
(~70h^{-1}_{50} Mpc) is roughly similar to the local ``Great Wall'', the area
may contain a high-redshift counterpart of superclusters in the local universe.
