An endoscope system and an operation method therefor in which information regarding a residual liquid is obtained to efficiently remove the residual liquid are provided. On the basis of image signals in a plurality of wavelength ranges, baseline information that is information regarding a light scattering characteristic or a light absorption characteristic of an observation target and that does not depend on specific biological information is calculated. A baseline correction value for adjusting the baseline information to reference baseline information that is a reference for evaluating the baseline information is calculated. From the baseline correction value, residual liquid information regarding a residual liquid included in the observation target is calculated.
