When designers begin a product design, they create their ideas and expand them. This process is performed on paper, and designers’ hand-drawn lines are called sketches. If the designers’ hand-drawn sketches can be realized as real curves, it would be effective in shortening the design period. We have developed a method to extract five degree Bezier curves based on a hand-drawn sketch. The basic techniques to detect curves based on a hand-drawn sketch are described. First, light intensity transformation, binarization of the hand-drawn sketch, and feature based erosion and dilation to smooth the edges of the binary sketch image are described. Then, line segment determination using the detected edges is described. Using the determined line segments a five degree Bezier curve generation is described. A curve shape modification algorithm is described to reconstruct a five degree Bezier curve. Examples of five degree fair curvature Bezier curves based on a sketch are given.