PROBLEM TO BE SOLVED: To provide an image processing device, an endoscope device, an image processing method, an image processing program, etc. capable of reducing a residual image and an artifact by noise reduction processing that takes into account a photographing condition.SOLUTION: An image processing device includes: an image acquisition part 315 a first noise reduction processing part 323 for creating a first image by subjecting a picked-up image to noise reduction processing in a time direction a second noise reduction processing part 324 for creating a second image by subjecting the picked-up image to noise reduction processing at least in a space direction a similarity detection part 321 for detecting a similarity between frames of the pick-up image a photographing condition acquisition part 322 for acquiring a photographing condition of the picked-up image and an image synthesizing part 325 for performing synthesis processing for the first image and the second image so that the higher the similarity is, the higher a synthesis degree of the first image is, and the lower a synthesis degree of the second image is, and changing the synthesis degree in the synthesis processing according to the photographing condition.
