Class II malocclusion can be treated via early orthopedic, orthodontic treatment or orthognathic surgery with orthodontic treatment. In the mixed dentition, early orthopedic treatment can be used. Especially, in the case of mandibular retrognathism, the functional appliances can be used, and in the case of maxillary protrusion is combined, they can be used together with headgear. After using activator and activator combined with headgear to the class II malocclusion paitent in the mixed dentition, the results were as follows: 1. Lateral profile was improved, and lower face height was increaed. 2. Overjet was decreased, and molar relationship was changed to class I molar relationship. 3. Growth can be undisturbed, and the aggravation of malocclusion can be prevented to make the 2nd phase orthodontic treatment be much easier.