Adhesive Composition and Pressure-Sensitive Adhesive Tape

An adhesive composition comprising a block copolymer (a) having a block mainly comprising a vinyl aromatic monomer unit, a tackifier (b) and an oil (c), wherein

• the block copolymer (a) comprises a partially hydrogenated block copolymer (a-1);
• the partially hydrogenated block copolymer (a-1) has a vinyl aromatic monomer unit and a conjugated diene monomer unit;
• a content of the vinyl aromatic monomer unit is 10 mass % or more and 19 mass % or less based on 100 mass % of the partially hydrogenated block copolymer (a-1);
• a hydrogenation ratio of double bonds contained in the conjugated diene monomer unit in the partially hydrogenated block copolymer (a-1) is 15 mol % or more and less than 80 mol % based on a total (amount) of double bonds before hydrogenation;
• when a ratio (P/O), which is a ratio of a content (P) of the block copolymer (a) to a content (O) of the oil (c), is 0.7 or more and less than 1.8, a ratio (T/O), which is a ratio of a content (T) of the tackifier (b) to a content (O) of the oil (c), is 1.0 or more and 4.0 or less;
• when the ratio (P/O), which is a ratio of a content (P) of the block copolymer (a) to a content (O) of the oil (c), is 1.8 or more and 6.0 or less, the ratio (T/O), which is a ratio of a content (T) of the tackifier (b) to a content (O) of the oil (c), is 2.1 or more and 8.2 or less;
• a content of the tackifier (b) is 60 parts by mass or more and 240 parts by mass or less based on 100 parts by mass of the block copolymer (a);
• and
• a content of the oil (c) is 10 parts by mass or more and 140 parts by mass or less based on 100 parts by mass of the block copolymer (a).