The ectopic eruption is defined rise to be abnormal eruption, which gives to displacement of the teeth and abnormal root resorption of adjacent teeth. The ectopic eruption of first permanent molar is approximately 2-4% of the population, most of them are in the maxilla, rarely in the mandible. In the case of the second permanent molars, most of them are found in the mandible for the reason of the arch length discrepancies and large size of the teeth. The ectopic erupted molars should be treated early in order to coordinate normal growth pattern and to obtain good occlusal support. So, this should be early diagnosed and treated. But, ectopically erupting molars are often self-corrected, hence periodic follow-up is required. The methods of the treatment are largely classified into surgical, surgical-orthodontic, and orthodontic method. Especially in orthodontic method, they are divided as follows; appliances that is positioned at the contact point for unlocking and the distal movement, fixed and removable appliance that is connected to more than one tooth, and occlusion guiding method after disking or extraction of the second deciduous molar. The report presents the good results in treating patients, whose chief complaint was ectopic eruption of mandibular permanent molars.