1. A work piece shape estimation device, comprising: an image information obtaining unit that obtains an image information by sensing multiple randomly accumulated work pieces having an identical shape; an edge detection unit that performs an edge detection on the image information obtained by the image information obtaining unit; a separating unit that separates the work pieces into partial images based on the image information obtained by the edge detection unit; a work piece categorization unit that categorizes the separated partial images of the work pieces; and an estimated work piece shape generation unit that generates an estimated shape of the work piece by complementing an information of the partial images of the work pieces categorized by the work piece categorization unit.