An inexpensive digitizing control device capable of producing a normal vector representing a normal direction of a model surface at real time by optical cutting method. A processor (11) of the control device (1) operates to move a table (31) with a model (6) horizontally with respect to a tracer head (4) on which a light source (5a) and a camera (56) are mounted. At the same time, measured data representing two detected points, where a light receiving pattern taken by the camera and two one-dimensional light sensors provided on a light receiving surface of the camera intersect each other, and table-camera movement control data are periodically subjected to sampling. Based on the sampled data, profile data are produced from coordinate values of two points on a model surface. A normal vector on the model surface is calculated based on the coordinate values of the two points and the coordinate value of the previously sampled point on the model surface in order to bring the tracer head to an angular position corresponding to the normal vector, so that a slit light is caused to fall into the camera positively.