An endoscope system comprises a light source, a light sensor, a signal processor, a video-signal generator, and a switcher. The light source emits red light including a first wavelength, green light including a second wavelength, and blue light including a third wavelength. The light sensor receives the light of the light source. The signal processor obtains a red signal based on the red light, a green signal based on the green light, and a blue signal based on the blue light. The video-signal generator generates video signal based on the red, green, and blue signals. The switcher switches between a first switching state and a second switching state. The red, green, and blue signals are output to the video-signal generator in the first switching state. The green and blue signals are output to the video-signal generator in the second switching state.