The endoscope apparatus includes a light exit that radiates an illumination light constituted by narrow-band lights to an observation target, an image sensor that detects a reflected/scattered light from the observation target to output an imaging signal, and an image processing circuit that processes the imaging signal. The image processing circuit includes an estimator that associates, regarding each color sensitivity region of the image sensor, a peak wavelength of the narrow-band light with the intensity of the reflected/scattered light to derive narrow-band light spectral intensity information, estimating wavelength lacking region spectral intensity information, and a processor that performs wavelength lacking region correction processing on the basis of the narrow-band light spectral intensity information and the wavelength lacking region spectral intensity information so that the image signal will be closer to an image signal obtained when an illumination light having no wavelength lacking regions is applied.