1. An image processing device comprising: a region-of-interest detecting unit that detects a region of interest from each of sequence images acquired in chronological order; a region dividing unit that divides a plurality of images temporally neighboring to each other into regions based on region-of-interest detection results obtained from the plurality of images; an inter-image variation calculating unit that calculates an inter-image variation between the plurality of images based on a variation in each region divided by the region dividing unit; and a display-condition setting unit that sets a display condition for each image based on the inter-image variation.