To provide a modified asphalt composition which is not separated, even when stored for a long time, and can be consistent with a balance with other required characteristics in a higher dimension.

This modified asphalt composition courprises 100 pts.wt. of asphalt, 2 to 20 pts.wt. of a high mol.wt. type thermoplastic elastomer having a number-average mol.wt. of 120,000 to 500,000, and 2 to 20 pts.wt. of a low mol.wt. type thermoplastic elastomer having a number-average mol.wt. of 80,000 to 100,000. Therein, the a high mol.wt. type thermoplastic elastomer is preferably a branched type polymer, and the low mol.wt. type thermoplastic elastomer is preferably a linear polymer.