An endoscope has a first light source section that emits white illumination light, a second light source section that emits narrow-band light, and an imaging section that captures a region to be observed by an imaging device having detection pixels of plural colors. The imaging section is caused to output a captured image signal including a return light component of the white illumination light from the region to be observed and a return light component of the narrow-band light from the region to be observed. Captured images of plural reference colors are generated based on the captured image signal. The captured images include a first captured image. Of the captured images, the first captured image contains the most return light component of the narrow-band light emitted from the second light source. A brightness level of the first captured image is changed independently from brightness levels of the other captured images.
