It has been known that adenomyoma is a rare non-neoplastic lesion of the biliary tract. In literature, adenomyoma was managed by extensive surgical procedures for its diagnosis and treatment because adenomyoma showed symptoms like obstructive jaundice and epigastric pain, which made the decision for the lesion difficult to distinguish from malignant neoplasm.We successfully treated a patient who had 12 mm sized adenomyoma of the major papilla with incomplete pancreas divisum by using an endoscopic papillectomy in the asymptomatic stage. The final diagnosis with an immunohistochemical stain revealed a lesion for adenomyoma of the major papilla.