An adhesive sheet which can actualize a high package reliability wherein there is no separation at the adhesive interface and no package cracking, in a package in which a semiconductor chip being reduced in thickness is mounted under severe reflow conditions after exposure to a hot and humid environment. The adhesive sheet includes a base material and, formed thereon, an adhesive layer having an adhesive composition including an acrylic copolymer (A) containing 20 to 95% by weight of a structural unit derived from a benzyl (meth)acrylate, an epoxy thermosetting resin (B), and a thermosetting agent (C).