Provided is a adhesive and an adhesive sheet which exhibit excellent chip-holding properties during dicing and from which chips can be easily stripped during pick up, even when considering changes over time. It is a adhesive composition which contains both (A) a (meth)acrylic acid ester copolymer component that has functional-group containing monomer units and a weight average molecular weight of less than 350,000 and (B) a (meth)acrylic ester copolymer component that has functional-group containing monomer units and a weight average molecular weight of 350,000 to 2,000,000 at a weight ratio of 10:90 to 90:10, and further contains 0.5 to 20 parts by mass of a crosslinking agent per 100 parts by mass of components (A) and (B) in total, the crosslinking agent being a crosslinking agent that reacts with both the functional groups of the component (A) and the functional groups of the component (B).