An endoscope system includes an optical transmission section that is provided in an endoscope inserted into an interior of a subject and transmits illuminating light to a distal end, a light source section that generates light, a first lens section that receives the light, from the light source section and emits the light with characteristics of different spatial intensity distributions, a second lens section that causes the light emitted from the first lens section to enter the proximal end of the optical transmission section, a distance adjusting section that can adjust a distance, and a control section that controls the distance adjusting section that adjusts the distance between the first lens section and the second lens section so that amounts of the light of a first and second wavelength bands have a predetermined ratio of amount of light.