To provide a novel cyclic conjugated diene copolymer excellent in cast film formation processibility, transparency, surface smoothness, and impact resistance; its production method; and a hydrogenation product of the cyclic conjugated diene copolymer.

The cyclic conjugated diene copolymer at least comprises repeating units derived from (A) a cyclic conjugated diene monomer and repeating units derived from (B) a linear conjugated diene monomer. The bonding structure containing A-derived units is a random structure comprising A-derived units and B-derived units; the polymer chain of the random structure has a number average mol.wt. of 10,000-500,000. The cyclic conjugated diene copolymer is produced by living anion polymerization, and its hydrogenated product is also provided.