A 49-year-old woman visited our hospital with dysphagia and chest pain. In another hospital, she was diagnosed as reflux esophagitis. Although she had taken proton pump inhibitor and prokinetics drugs for a long time, she was not relieved of any symptoms. On the basis of high resolution manometry and endoscopic ultrasonography findings, Jackhammer esophagus was diagnosed. In this patient, peroral endoscopic myotomy (POEM) was performed for long myotomy of thickened circular muscle. During the procedure, there were no significant complications and she was discharged uneventfully. Symptoms were completely improved during three months after POEM. Here, we report on a case of Jackhammer esophagus treated by POEM.