Adhesive composition and adhesive sheet

The invention provides an adhesive composition and an adhesive sheet. Provided is an adhesive composition capable of forming an adhesive having both rough surface adhesiveness and high-temperature holding power, and having good storage properties. Provided is an adhesive composition containing: a block copolymer of a monovinyl-substituted aromatic compound and a conjugated diene compound; a tackifying resin; and a softening agent. In the adhesive composition, the tackifying resin contains a natural tackifying resin (A) which has a softening point of more than 80 DEG C and does not contain an aromatic ring and a petroleum tackifying resin (B) which has a softening point of more than 100 DEG C and contains an aromatic ring. In addition, the content of the tackifier resin (A) is 40-120 parts by weight per 100 parts by weight of the block copolymer. The content of the tackifier resin (B) is 5-40 parts by weight per 100 parts by weight of the block copolymer. The total amount of the tackifier resin is 60-160 parts