Spiral unit and introduction apparatus

A spiral unit into which an insertion section of an introduction apparatus having a longitudinal axis is to be inserted, and is rotatable to the insertion section in a state of being disposed on the insertion section, the spiral unit comprising:

• a tube body which is configured to be arranged along the longitudinal axis, and has a spiral fin arranged on an outer peripheral surface thereof;
• a tubular section which is provided on at least one of a distal end side and a proximal end side of the tube body along the longitudinal axis, has a proximal part close to the tube body and a distal part apart from the tube body, has an outer periphery that is diameter-reduced toward the longitudinal axis more at the distal part than at the proximal part along the longitudinal axis, and exerts a diameter reducing force to an outer peripheral surface of the insertion section at the distal part in the range where sliding is possible in a periaxial direction of the longitudinal axis;
• and
• a regulator which is removably arranged in the tubular section, holds a state of expanding an inner diameter of the tubular section to regulate reduction of the inner diameter of the tubular section.