The insertion device includes an insertion portion that is inserted into a lumen, a fixing portion that is provided at an insertion part of the insertion portion to be inserted into the lumen, and fixes the insertion portion at a first position inside of the lumen, and a positioning portion that is attached to a part of the insertion portion exposed to the external of the lumen and provided in the outer part of the lumen. The positioning portion positions the insertion portion at a second position outside of the lumen.