1. An image processing device comprising: circuitry configured to calculate a matching degree between a pixel value of a target pixel in a standard image of a current frame and a pixel value of a corresponding pixel in a reference image of the current frame; and estimate a disparity between the standard image and the reference image based on a result obtained by calculating the matching degree, wherein the circuitry calculates the matching degree using a disparity estimated for the standard image and the reference image of a previous frame, the circuitry calculates a temporal evaluation value used to evaluate a temporal variation in a disparity based on a difference between the disparity for the previous frame and the disparity estimated for the standard image and the reference image of the current frame, and the circuitry calculates the matching degree using the temporal evaluation value.