This paper presents a method for constructing a surface model automatically from a single sketch image. A sketch image is drawn on a paper based on some rules of design presentation drawing. From the sketch image which is digitized by a scanner, a contour image is got in advance. The process of our presented method consists of the following three stages. Firstly, 2-D vertices are detected from the contour image, and 3-D coordinates of vertices are inferred from 2-D coordinates. Secondly, an adequate wire-frame model is constructed using cubic Bézier curves by moving each inferred vertex to an optimum location. The shape of a wire-frame model is optimized using genetic algorthm so that the projection of the wire-frame model to the image plane coincides with the contour of the sketch image. Finally, a surface model is constructed using bicubic Bézier surfaces by interpolating the wire-frame model.