An endoscope system includes an imaging section that includes an optical system and an imaging element, an observation mode setting section that sets an object observation mode, a diaphragm control section that selects a diaphragm state based on the observation mode, and an image processing section that processes an image acquired by the imaging section. The diaphragm control section selecting a first diaphragm state when the observation mode is a first observation mode. The first diaphragm state being a state in which a resolution determined by a diffraction limit based on a diaphragm of the optical system is lower than a resolution determined by the imaging element. The diaphragm control section selecting a second diaphragm state when the observation mode is a second observation mode. The second diaphragm state being a state in which the resolution determined by the diffraction limit based on the diaphragm of the optical system is equal to or higher than the resolution determined by the imaging element.