To obtain a norbonene-based film excellent in optical properties such as transparency and free from strength deterioration caused by thermal decomposition during extrusion.

This norbornene-based film has a weight-average molecular weight of ≥80,000 and ≤140,000, a molecular weight distribution obtained by dividing the weight-average molecular weight with a number-average molecular weight of ≥4 and ≤6, and a thickness of ≥0.05mm and ≤0.3mm. This film is produced by melt extrusion under the following conditions: a T-die or a coat hunger die is used on extrusion by an extruder; the retention time in the extruder is ≥15min and ≤30min; both of the cylinder temperature and the die temperature of the extruder are ≥280°C and ≤320°C.