PROBLEM TO BE SOLVED: To provide an assistive tool for an endoscope for favorably performing an observation restricted with a transnasal endoscope in such a way that a monitor screen is dark, and to provide an endoscope system with the assistive tool.SOLUTION: An assistive tool 153 is used together with a transnasal endoscope 11 having an insertion part inserted from one of external nostrils, and has an insertion part inserted from the other external nostril. A plurality of LEDs 154 for white illumination are provided at a leading end of the insertion part. The LEDs 154 are arranged such that light emitting parts are exposed from a leading end surface 38a of the insertion part. The LEDs 154 emit light within a body cavity for exposing illumination light, thereby assisting the illumination function for the transnasal endoscope 11.
