This is a multi-center, randomized, double blinded, active controlled, parallel-group study to evaluate the immunogenicity and safety of three different potencies of NBP608(low, middle, high potency) and Varivax which are indicated for active immunization for the prevention of varicella. Total of 152 subjects (38 subjects per each treatment arm) of 12 months to 12 years of age are enrolled, and each subject is administered with single dose of vaccine which is randomly assigned in 1:1:1:1 ratio. Stratified randomization for age group is used to achieve the balance of treatment assignment within age strata.