An adhesive composition for semiconductor device, comprising 10 to 30% by weight of a reactive elastomer (A), 40 to 65% by weight of an epoxy resin (B) having two or more glycidyl ether groups, a phenol resin (C) and a curing accelerator (D), wherein a ratio of the epoxy resin (B) to the phenol resin (C) is within a range from 1:0.6 to 1:1 in terms of a functional group equivalent ratio, and an adhesive sheet for a semiconductor device using the same are provided. The composition and the sheet are superior in reflow resistance and short-time and low-temperature bonding without lowering characteristics such as heat resistance, low hygroscopicity, high adhesion and electrical insulating properties of an epoxy resin cured article.