To provide a pressure-sensitive adhesive composition which exhibits an excellent opacifying capability without detriment to pressure-sensitive adhesive properties of an acrylic pressure-sensitive adhesive even when a substrate sheet is transparent or even when the pressure-sensitive adhesive layer is thin; and a pressure-sensitive adhesive sheet using the same.

This pressure-sensitive adhesive composition contains a copolymer consisting mainly of structural units derived from an alkyl (meth)acrylate monomer, a particle-surface-treated aluminum powder having an average particle size of 5-50 μm and an aspect ratio of 50-200, and titanium oxide. The pressure- sensitive adhesive sheet is prepared by using the composition.