To provide a new cyclized copolymer having all the excellent heat resistance, transparency and melt moldability and to provide a method for producing the same.

The cyclized copolymer is obtained by polymerizing a norbornene-based monomer (norbornenes or tetracyclododecenes) with a non-conjugated diene compound in the presence of a specific polymerization catalyst represented by (Cp)2M2Z1pL1q and has a cross-linked alicyclic repeating unit and an alicyclic repeating unit. Furthermore, the cyclized copolymer has 1,000-1,000,000 weight-average molecular weight. The method for producing the copolymer is provided.