Inclusion Criteria:

1. Male or female patients between 20 and 80 years

2. Patients with a diagnosis of RLS according to the following diagnosis criteria of NIH/IRLSSG:

   1. An urge to move the legs, usually accompanied or caused by uncomfortable and unpleasant sensations in the legs.
   2. The urge to move or unpleasant sensations begin or worsen during periods of rest or inactivity such as lying or sitting.
   3. The urge to move or unpleasant sensations are partially or totally relieved by movement, such as walking or stretching, at least as long as the activity continues.
   4. The urge to move or unpleasant sensations are worse in the evening or night than during the day or only occur in the evening or night.
3. Patients with a total score larger than 15 on the RLS rating scale at Visit 2

Exclusion Criteria:

1. Premenopausal women who meet any of the following 1) to 3) 1) Patients who are pregnant or possibly pregnant 2) Patients who are lactating 3) Patients who wish to become pregnant during the study period
2. Patients who cannot take adequate contraceptive measures
3. Patients with a history of akathisia induced by neuroleptics
4. Patients with diabetes mellitus requiring insulin therapy
5. Patients who are judged to have microcytic anaemia by the investigator or sub-investigator
6. Patients with a history or signs of peripheral neuropathy, myelopathy, multiple sclerosis, Parkinson?s disease or other neurological diseases that may result in the occurrence of secondary RLS in the physical function tests or neurological tests
7. Patients with other sleep disorders such as abnormal behaviour during REM sleep, narcolepsy and sleep apnoea syndrome (patients with an apnoea-hypopnoea index (AHI) exceeding 15 determined by polysomnography at the relevant trial site or those with loud snoring at least 5 nights/week and an experience of respiratory arrest during sleep or excessive daytime sleepiness)