Endoscope

An endoscope comprising:

• a front end portion at which an image pick-up unit which has an optical system which changes an image-formation range by focusing by displacing at least a part of a lens group, is disposed, wherein
• in a driving mechanism which displaces the range group to be displaced, a shape memory element which is displaced by heating is let to be a driving force, and a displaceable range of the lens group is restricted between a first position and a second position, and
• with the shape memory element in a heated state by imparting a predetermined amount of heat to the shape memory element, the lens group to be displaced is displaced to the first position, and when the shape memory element is not heated, the lens group to be displaced is displaced to the second position,
• during a normal observation, a time for which the position of the lens group to be displaced is displaced to the second position is longer than a time for which the position of the lens group to be displaced is displaced to the first position;
• and
• a bending portion which can be bent, and which is connected to the front end portion, wherein
• the shape memory element is interpolated into a tube member which can be bent, and the shape memory element and the tube member are extended to the bending portion, and the tube member and the shape memory element are coupled at an end portion of the tube member, toward the bending portion, and the other end of the tube member is fixed to a predetermined part of the front end portion, and the other end of the shape memory element is fixed to the lens group to be displaced.