Method of manufacturing an elbow, cutting tool, and elbow

A method of manufacturing an elbow, comprising:

• a cutting step of cutting a roughly formed elbow to form an inner side surface of the elbow to be finished by relatively moving a cutting section included in a cutting tool, which is formed of at least a part of a substantially spherical shape, along a center line of the elbow to be finished in a direction from a first end surface to a second end surface of the roughly formed elbow;
• a moving step of relatively moving the cutting section along the center line of the elbow to be finished in a direction from the second end surface to the first end surface of the roughly formed elbow;
• and
• an outer side surface formation step of forming an outer side surface of the elbow to be finished by carrying out cutting along an outer circumference of an outer side surface of the roughly formed elbow by relatively rotating a processing tip, and moving the roughly formed elbow in the direction from the first end surface to the second end surface,
• the cutting section having a diameter substantially equal to an inner diameter of the elbow to be finished,
• wherein the roughly formed elbow has a through-hole penetrating from the first end surface to the second end surface, and based on the cutting step, a first position of contact between the roughly formed elbow and the cutting section is separate from a second position of contact between the roughly formed elbow and the cutting section, in a direction along a shaft section extending from the cutting section.