With the instrument here described the gravity anomaly caused by an arbitrarily given finite body can be computed. The integrator is operated by tracing the contour lines representing the body in a manner similar to the operation of a planimeter. The instrument is useful mainly in the indirect method of interpretation of observed gravity anomalies, in the computation of terrain corrections, and in the evaluation of magnetic anomalies. Its design is based on a formula which expresses the gravity anomaly caused by an infinitely thin slab, bounded by a closed curve, as a line integral over this curve.