To provide a polymer which shows an improvement in processability along with improved physical properties and dynamic properties, to provide a manufacturing method thereof, and to provide the use thereof for manufacture of all the types of rubber moldings, particularly for the manufacture of tires and tire-constituting materials such as tire treads.

The polymer is modified with a functional terminal group, and is based on a conjugated diene or based on a conjugated diene and a vinyl aromatic compound, and has an average mol.wt. (Mw) exceeding 10,000 g/mol and a mol.wt. distribution (Mn/Mw) of 1.3-5.