An endoscope system includes: a light source unit generating illumination-light； an image sensor that images an observation target using the illumination-light in a unit of an imaging frame including an accumulation period and a readout period； a light source control unitchanging the wavelength band or the spectrum of the illumination-light for each imaging frame； an image processing unit that generates one observation image using a plurality of captured images acquired in a plurality of imaging frames having different wavelength bands or different spectra of the illumination-light； and an imaging control unit that keeps constant a total time of the accumulation period and the readout period of the plurality of imaging frames for acquiring a plurality of captured images used in generating the observation image and that extends or shortens the length of the accumulation period or the readout period of each of the imaging frames in the constant total time.
