1. An endoscope apparatus comprising: a light source unit that is capable of adjusting quantity of light and irradiates illumination light to a subject; an imaging element that captures a capturing image by return light from a living body that is the subject in the illumination light and outputs a captured image signal; a density calculating section that calculates density of each pixel of the captured image on basis of the captured image signal; and an image processing section that performs a predetermined image processing on the captured image, wherein the image processing section changes frequency processing conditions with respect to the captured image such that detection and enhancement degree of a structure and components of the living body in the subject are changed according to at least the density of each pixel of the captured image.