1. A work piece shape estimation device, comprising: an image information obtaining unit configured to obtain image information without access to CAD data by capturing an image of multiple randomly accumulated work pieces that overlap one another, wherein the work pieces are identical to one another in shape; an edge detection processor configured to perform an edge detection on the image information obtained by the image information obtaining unit; a separating processor configured to separate the work pieces into partial images based on the image information obtained by the edge detection processor; a work piece categorization processor configured to categorize the separated partial images of the work pieces into different categories by performing pattern matching on each of the respective partial images and by organizing the partial images based upon a shape of each of the respective partial images, wherein the work piece categorization processor arranges the partial images within each of the different categories based upon an area of each of the partial images; and an estimated work piece shape generation processor configured to generate an estimated shape of the work piece by complementing an absent portion of the partial images of the work pieces categorized by the work piece categorization processor, wherein the estimated work piece shape generation processor generates the estimated shape of the work piece by selecting one of the different categories so as to define a selected category and selecting the partial image within the selected category that has a greatest area of all of the partial images within the selected category so as to define the largest partial image, and wherein the estimated work piece shape generation processor superimposes the partial images from the selected category on top of the largest partial image in order of decreasing area.