A non-contact tracing control apparatus is disclosed which traces the surface of a model by using at least two optical distance detectors for detecting the distances therefrom to the model. When a first light corresponding to a first of the optical distance detectors is detecting a distance, a second light of another, second optical distance detector is either dimmed or shut off. Interference between more than one light reflected from the model and errors from, i.e., the first light reflected from the model incident on a second position sensor of the second optical distance detector can be avoided. The distances to a plurality of measurement points thus can be detected without interference even though the measurement points on the surface of the model are relatively close to one another.