PROBLEM TO BE SOLVED: To provide an endoscope system capable of properly transmitting in vivo image information regardless of an environment around an imaging device.SOLUTION: An endoscope system 1 includes: an endoscope 2 having an imaging element 244 for outputting electric signals after photoelectric conversion from a plurality of pixels as image information and a transmission part for converting the image information output by the imaging element 244 to optical signals and transmitting them to the outside and a processor 3 connected to the endoscope 2, and capable of transmitting and receiving the optical signals to/from the endoscope 2. The processor 3 includes a control part 309 for controlling transmission output characteristics of the optical signals when the transmission part 246 transmits the optical signals to the outside.
