An endoscope system includes an imaging section that captures an object via an optical system and an image sensor, an observation state determination section that determines the observation state of the object captured by the imaging section, and an aperture control section that controls the state of an aperture included in the optical system based on the observation state, the aperture control section controlling the state of the aperture so that the resolution determined by the diffraction limit due to the aperture is equal to or higher than a resolution determined by the image sensor when the observation state determination section has determined that the observation state is a first observation state, and stopping down the aperture as compared with the state of the aperture in the first observation state when the observation state determination section has determined that the observation state is a second observation state.
