Provided are an asphalt modifier comprising a vinyl aromatic hydrocarbon-conjugated diene block copolymer of Formula 1 and an asphalt composition comprising the asphalt modifier. A ˆ’ B ˆ’ C n ˆ’ D (where A, B, C, D, and n are the same as defined in the specification) The asphalt modifier comprising the vinyl aromatic hydrocarbon-conjugated diene block copolymer of Formula 1 may improve low-temperature and high-temperature physical properties when used in the asphalt composition, and since the asphalt modifier may also reduce dissolution time by increasing a dissolution rate, storage stability of the asphalt composition may be improved.