An image processing device, an endoscope apparatus, an image processing method, an image processing program, and the like make it possible to perform an appropriate enhancement process corresponding to the observation state. The image processing device includes an image acquisition section (310) that acquires a captured image that includes an image of an object, a distance information acquisition section (380) that acquires distance information based on the distance from an imaging section to the object when the imaging section captured the captured image, a known characteristic information acquisition section (390) that acquires known characteristic information that is information that represents known characteristics relating to the object, and an enhancement processing section (370) that performs an enhancement process that corresponds to the distance information based on the known characteristic information.
