This study design is A Randomized, Double-blind, Multi-center, Phase II Optimal Dose-finding Study to Determine the Safety and Efficacy of Meditoxin® in Subjects in Benign Masseteric Hypertrophy.

Subjects who voluntarily signed the informed consent and are judged to be eligible for this study will be intramuscularly injected with the study drug or the placebo to find appropreate dose for the treatment of Benign Masseteric Hypertrophy. Thereafter, follow-up visits will be made and efficacy and safety assessment will be conducted.

Inclusion Criteria:

1. Subject who shows benign masseteric hypertrophy
2. Male or female subject over 19 years of age and written informed consent is obtained from the patient or LAR.
3. Subject who has bisymmetry of masster at visual assessment.
4. Subejects who qualifies the standard meets on ultrasonics wave value.
5. Subjects who can and will comply with the requirements of the protocol.

Exclusion Criteria:

1. Diagnosis of myasthenia, facial palsy or severe facial asymmetry
2. Subject who got any treatment, including double jaw surgery, laser, thread treatment etc. in 1 year.
3. Subject who had previously received botulinum toxin within 3 months prior to the study entry
4. Subject who is participating in other investigational study at present or 30 prior to the screening date.
5. Subject with known hypersensitivity to botulinum toxin
6. Subject who are pregnant or lactating or found pregnancy though the urine or sebum test or disagreed to avoid pregnancy during study preiod.
7. Subjects who are not eligible for this study at the discretion of the investigator.