Achalasia is a motility disorder of the esophagus characterized by absence of peristalsis and failure of relaxation of lower esophagus sphincter. The introduction of high resolution manometry (HRM) and per-oral endoscopic myotomy (POEM) has made a new chapter in diagnosis and treatment of achalasia. HRM allows classify according to the subtype of achalasia, and help predict prognosis and therapeutic response. POEM is a minimally invasive, effective option for treating achalasia. The management of achalasia required tailored application of various therapies such as botox injection, pneumatic balloon dilatation, POEM, or Heller’s myotomy. In this review, we state the important aspects of diagnosis as well as management of achalasia. (Korean J Gastroenterol 2019;73:294-298)