A bicyclic conjugated diene polymer obtained by polymerizing a monomer (M) comprising at least one kind of bicyclic conjugated diene monomer represented by formula (I), and a bicyclic conjugated diene copolymer obtained by copolymerizing monomer (M) with at least one kind of unsaturated compound other than said monomer: ##STR1##

wherein, R₁ to R₆ are the same or different and are each hydrogen, halogen, or alkyl or halogenated alkyl of 1 to 20 carbon; n and m are each an integer of from 0 to 10; X₁, X₂, Y₁ and Y₂ are the same or different from each other and are each hydrogen, halogen or alkyl or halogenated alkyl of 1 to 20 carbon; and, when m or n is 2 or more, each of mX₁'s, mX₂'s, nY₁'s and nY₂'s are the same or different.