Abstract: A pattern matching unit carries out a pattern matching between a photographed image obtained by photographing a workpiece with a monocular camera and a first plurality of models having a plurality of sizes and a plurality of angles, and selects a model having a size and an angle with the highest degree of matching. A primary detection unit detects a position and an angle of an uppermost workpiece based on the selected model. An actual load height calculation unit calculates an actual load height of the uppermost workpiece based on a hand height. A secondary detection unit re-detects the position and the angle of the uppermost workpiece based on a model having a size and an angle with the highest degree of matching selected by carrying out a pattern matching between the photographed image and a second plurality of models selected or newly created based on the actual load height.