When light reflected off a treatment tool and light reflected off an organ during in vivo observation are equal in brightness and wavelength, both the treatment tool and organ appear clear with an unwanted object acting as a disturbing element. Also, there is a problem in that a desired object cannot be observed conversely in amniotic fluid due to high transparency when fiber is used alone. A treatment tool is made of transparent material, provided with illuminating light for treatment tool observation differing at least partially in wavelength from illuminating light for in vivo observation, and configured to allow intensity to be adjusted independently. Visibility of the treatment tool in a wavelength range of the illuminating light for treatment tool observation is configured to be higher than visibility of the treatment tool in a wavelength range of the illuminating light for in vivo observation.
