A pressure-sensitive adhesive, and a pressure-sensitive adhesive sheet

Acrylic polymer (A), a pressure-sensitive adhesive containing an acrylic oligomer (B), and cross-linking agent (C), the weight average molecular weight of the acrylic polymer (A) is 400,000 2,000,000 acrylic oligomer (B) comprises an alicyclic group-containing (meth) acrylate monomer (b1) derived from the structural unit (b1), and have a weight average molecular weight of 1,000 to 50,000, the content of the acrylic oligomer (B) , the acrylic polymer (a) 1 to 45 parts by weight in which the adhesive and the adhesive sheet relative to 100 parts by weight has excellent interfacial adhesion regardless of the level of polarity, excellent in durability and transparency.