This paper proposes an optimization model for the network service mapping and scheduling problem with uncertain processing time. We model processing time uncertainty through Gamma-robustness approach, which provides different degrees of robustness against processing time uncertainty. We formulate the problem with the objective to minimize the worst-case makespan over the given uncertainty set. A heuristic is presented to tackle the problem. The numerical results show that the proposed model outperforms the conventional model with deterministic parameters in terms of worst-case makespan.