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; estimate a disparity between the standard image and the reference image based on a result obtained by calculating the matching degree; and calculate a spatial evaluation value used to evaluate a spatial variation in a disparity based on a difference between a disparity estimated for a neighboring pixel located near the target pixel and a disparity estimated for the target pixel, wherein the circuitry calculates the matching degree using the spatial evaluation value and a disparity estimated for the standard image and the reference image of a previous frame.