In this paper, a method to simulate deformation of a shield braid of a cable, which is useful for predicting its lifespan, is proposed. A shield braid in a shielded cable used in a robot may break due to repetitive movement of the robot. For avoiding that, the lifespan of the shield braid must be known. However, fatigue testing to measure its lifespan requires much time and cost. Predicting the lifespan of a shield braid by simulation would reduce such time and cost. As a shield braid is composed of many strands, each strand is modeled based on the differential geometry at first. After that, a method to predict the shape of one strand from that of another strand adjacent is proposed for reduction of computation time. Then, the deformed shape of the whole braid can be simulated when a shield cable is bent. Furthermore, strain at any point on the braid can be estimated from the deformed shape of the braid simulated. Estimated strain is useful for prediction of the lifespan of the braid when the cable is bent repeatedly.