The polymer according to the present invention is a polymer containing a conjugated diene monomer unit and a vinyl aromatic monomer unit, wherein the polymer has a polymer block (A) containing the vinyl aromatic monomer unit as a main component and a polymer block (B) containing the conjugated diene monomer unit and the vinyl aromatic monomer unit, a content of the polymer block (A) is 10 % by mass or more and 40 % by mass or less, a bulk density of the polymer is 0.05 g/mL or more and 0.45 g/mL or less, and a specific surface area of the polymer is 0.10 m 2 /g or more and 0.60 m 2 /g or less.