An image processing device includes: an image acquiring unit configured to acquire a plurality of images at different imaging time which images are captured when illumination light in different wavelength bands is emitted； and a processor including hardware. The processor is configured to generate a low-resolution image by lowering resolution of at least one image in the plurality of images, and detect light-absorption information at a certain depth based on a correlation between images which are in an image group including the low-resolution image and the plurality of images, which are captured with the illumination light in different wavelength bands, and at least one of which is the low-resolution image.
