An endoscope system includes an insertion portion, an optical transmission section that is provided in the insertion portion and transmits illuminating light incident on a proximal end to a distal end, a light source section that generates light of a first wavelength band and light of a second wavelength band, a first lens section that receives, as incident light, the light of the first wavelength band and the light of the second wavelength band from the light source section and emits the light with characteristics of different spatial intensity distributions in accordance with wavelengths, a second lens section that is provided opposite to the first lens section and causes the light emitted from the first lens section to enter the proximal end of the optical transmission section, a distance adjusting section that adjusts a distance between the first lens section and the second lens section, and a control section that controls the distance between the first lens section and the second lens section so that an amount of the light of the first wavelength band and an amount of the light of the second wavelength band emitted from the distal end of the optical transmission section have a predetermined ratio of amount of light.
