The present invention addresses the problem of providing an orthodontic retainer with which there are no aesthetic concerns and smooth pronunciation during conversation is possible, and which is able to secure favorable fitting and can be worn for long periods. The retainer is configured so that, by being fitted so as to surround the entire dental arch (T) of the maxilla (A) or the mandible and by the inner surface being fitted, on the front and back surfaces of the entire dental arch (T), with a specified vertical width (H) that encompasses the cervical sections (T1, T2) of said teeth, a retaining force is applied on a portion of the crown (T3) of each tooth from the front and back surfaces.