The purpose of this study is to test the hypothesis that the efficacy and safety of Meditoxin® are not inferior to Botox®'s in the treatment of Cervical Dystonia.

The allocated subject is injected Investigational Product(Meditoxin® or Botox®) 200~300U in cervical muscles. The efficacy and safety are evaluated for 12weeks through 4 follow up visits.

Inclusion Criteria:

• Men and women aged between 20 and 75.
• Patient who is diagnosed with primary cervical dystonia over 1 year.
• Patients whose total score is over 20 in TWSTRS and the severity score is over 10 in TWSTRS.
• For patients with prior treatments of Botox®, over 12 weeks have passed.
• Patients who voluntarily sign the informed consent
• Patients who can comply with the study procedures and visit schedule

Exclusion Criteria:

• Patient who has been diagnosed with pure anterocollis.
• Patient who has been diagnosed with neuromuscular disorder(myasthenia gravis, Eaton-Lambert syndrome, amyotrophic lateral sclerosis, etc.)\
• Severe respiratory function disorder or dysphasia
• Allergy in Investigational Product.
• Pregnant women, breast feeding women and patients disagreeing to use an acceptable contraception method
• Investigator's decision.