There are provided a pressure-sensitive adhesive composition containing stably dispersed metal-based fine particles, having further reinforced mechanical properties, and being capable of forming a pressure-sensitive adhesive layer with excellent refractive index and excellent adhesive strength, and a pressure-sensitive adhesive sheet produced therewith. A pressure-sensitive adhesive composition is prepared which includes as a monomer component 100 parts by weight of a (meth)acrylic polymer including 50% by weight or more of a (meth)acrylate represented by the formula CH2═C(R1)COOR2, wherein R1 represents hydrogen or a methyl group, and R2 represents a substituted or unsubstituted alkyl group of 1 to 20 carbon atoms, having a weight average molecular weight of 500,000 to 3,000,000 as determined by gel permeation chromatography, and being substantially free of an acid component; 5 to 100 parts by weight of a low-molecular-weight aromatic polymer having a weight average molecular weight of 500 to 4,000 as determined by gel permeation chromatography; and 5 to 100 parts by weight of metal-based fine particles having an average particle size of 5 to 100 nm.