This is a Phase III, multicentre, randomised, double-blind, placebo-controlled study to evaluate the effects of 100 mg safinamide, administered orally once daily (OD), in Chinese Parkinson's disease (PD) patients, experiencing motor fluctuations while on stable doses of Levodopa (L-dopa) (alone or in combination with other anti-Parkinson drugs). Eligible patients are required to meet the United Kingdom PD Society Brain Bank Clinical Diagnostic Criteria. The study involves a placebo group. Placebo will be added to the standard stabilized treatment as a control of the safinamide group, hence patients on placebo will have benefit from other ongoing anti-PD medication. A total of 306 patients will be randomised into this study (153 in the safinamide and 153 in the placebo groups).