An endoscope 100 includes a first light source 45 that emits white illumination light, a second light source 47 that emits narrow-band light and an imaging section that has an imaging device 21 having plural detection pixels and images a region to be observed. The imaging section is caused to output a captured image signal including both a return light component of the white illumination light from the region to be observed by and a return light component of the narrow-band light the white illumination light. From the captured image signal, the return light component of the narrow-band light is selectively extracted, and a brightness level of the extracted return light component of the narrow-band light is changed by changing a light amount of light emitted from the second light source 47.