To provide an asphalt composition for a casting type joint sealing material or a roofing material for rooftop, wherein the asphalt composition can significantly improve the physical properties of asphalt, is excellent in workability, and can achieve good weatherability in the coating film obtained.

The asphalt composition used for a casting type joint sealing material or a roofing material for rooftop comprises a mixture of asphalt and rubber powder. Fine rubber powder having a particle size passing through an 80 mesh (0.175 mm) sieve is used as the rubber powder. The amount of the rubber powder to be mixed in the asphalt composition is preferably within the range of 10-30 wt.%.