A preprocessing device includes processing circuitry configured to acquire coordinate information of respective vertexes of a polygon for inside/outside determination and the coordinate information of the respective vertexes of the polygon for inside/outside determination and rotate a coordinate to be determined and the polygon for inside/outside determination as preprocessing of determination processing of determining whether the coordinate to be determined exists inside or outside the polygon for inside/outside determination, and output coordinate information of respective vertexes of the rotated polygon for inside/outside determination and the rotated coordinate to be determined as rotated coordinate information.