1. A data processing device for, based on an image received as input, estimating pose of an object of pose estimation with respect to a reference surface that serves as a reference for estimating pose, said data processing device comprising: a binarization unit for dividing said image into a candidate region that is a candidate for said reference surface and a background region that is a region other than the candidate region; a surface parameter formula expression unit for extracting pose parameters that indicate the pose of an object of pose estimation with respect to a reference surface that appears in said image that was received as input and, based on the combination of a value obtained by implementing transform by a prescribed function upon, of the pose parameters that were extracted, parameters that indicate a direction in which the object of the pose estimation is directed and pose parameters other than the parameter that indicate direction, finding surface parameter formulas that are numerical formulas that express said reference surface; an all-candidate surface drawing unit for, based on the combination of all pose parameters in parameter space, which is space having, as the axes of base vectors, each of the parameters included in said pose parameters, drawing candidate surfaces that accord with said surface parameter formulas on said image in said parameter space; a cross determination unit for, as regards each candidate surface that was drawn by said all-candidate surface drawing unit, identifying pixels that are located on, of said candidate region, the candidate surface, and pixels that are located within a prescribed range from the candidate surface as cross pixels and finding coordinates of the cross pixels and tangent planes at said cross pixels; a weighting computation unit for, based on angles that are formed by tangent planes at the cross pixels that were found by said cross determination unit and planes that are formed by the axes of each base vector included in said parameter space, finding a slope weighting for each cross pixel that was identified by said cross determination unit; a number measurement unit for computing for each of said candidate surfaces a number that is the value obtained by adding up the slope weightings of cross pixels that were found by said weighting computation unit that were contained in each of the candidate surfaces; and an actual surface determination unit for, based on the number computed by said number measurement unit, identifying from among candidate surfaces drawn by said all-candidate surface drawing unit an actual surface that is a reference surface that actually exists in said image.