An endoscope system includes: an endoscope configured to have a field of view in front of a distal end portion of an insertion portion having flexibility and an elongated shape an insertion assisting instrument including a conduit having an inner portion through which the insertion portion can be inserted, and the insertion assisting instrument being configured to enable an angle of a distal end portion of the conduit to be changed an image generation section that generates an image corresponding to the field of view of the endoscope and outputs the generated image a rotation angle calculation section that calculates a rotation angle indicating to what extent an orientation of the image is rotated with respect to a reference direction, the image being outputted from the image generation section when at least a part of the insertion portion is inserted through the conduit and an image rotation section that performs image rotation processing on the image outputted from the image generation section, for displaying, on a display screen of a display section, the image with the rotation angle being offset.
