An endoscope apparatus includes a light source device, an endoscope, a processor, and an observation monitor. The light source device switches between excitation light EX that excites a connective tissue in a submucosa of a tissue within a body cavity, narrow-band light NBa absorbed by a blood vessel running through the submucosa or muscularis propria, and narrow-band light NBb absorbed by a substance locally injected into the submucosa, and radiates the selected light. The processor generates a plurality of image signals, images of which are picked up by a CCD of the endoscope and the observation monitor synthesizes a plurality of images and displays the synthesized image.
