Operability in inserting an insertion part of an endoscope into a body cavity using an insertion assisting tool is improved. In an insertion assisting tool, a sidewall portion of a tube main body through which an insertion part of an endoscope is passed is provided with a sidewall opening part having a size in which the insertion part can pass through. A distal end side of the sidewall opening part is provided with a guiding valve, and the insertion part is guided by the guiding valve to be easily fed from the sidewall opening part. The guiding valve is swingably supported, and when the insertion part is fed from a distal end opening part of the tube main body, allowing the parallel state of being substantially parallel to an axial direction of the insertion part and passing the insertion part to a distal end opening part side are enabled.