An endoscope system includes an illuminator configured to switch between a first illumination light and a second illumination light for which a ratio of a quantity of light is 1/α, an objective optical system, an image sensor, an optical path splitter which is disposed between the objective optical system and the image sensor, the optical path splitter has an optical path splitting surface, a first reflecting surface, and a second reflecting surface. A processor acquires for each of the first illumination light and the second illumination light, a first image pickup signal and a second image pickup signal, combines the first image pickup signal and the second image pickup signal for the first illumination light and the first image pickup signal and the second image pickup signal for the second illumination light, and generates an image of a high dynamic range. Here, α denotes a coefficient.