To provide a method for producing a transparent polymer having a high refractive index and a high Abbe's number and useful for an optical lens by polymerizing a compound having plural specific cyclopentadieno groups and a compound having plural specific cycloalkenyl groups at a high temperature.

The objective polymer is obtained by polymerizing (A) a compound having two or more cyclic conjugated dieno groups having no readily eliminable substituent, at the terminals and (B) a compound having two or more cycloalkenyl groups in which a part of C atoms forming a ring can be substitsuted with a hetero atom by a cycloaddition reaction. For example, when bis{4-(1'-methoxy-1',2',3',4'-tetrachlorocyclopenta-2',4'-dieno)oxyphenyl}sulfide is used as the component A, and bis{4-(N-maleimide)phenyl}sulfide is used as the component B, the resultant polymer has 1.598 refractive index and 33.0 Abbe's number, and also has a good transparency.