This paper discusses cyber attacks and faults diagnosis method for networked electrical power systems. In this paper, a power system is divided into some areas, and then, some parameters are estimated by Kalman filter in each area. Then we propose a diagnosis method by using called state and output fault diagnosis matrices which are composed of the estimated values, output matrix and so on. These diagnosis matrices can immediately judge which nodes of which area is attacked. Finally, some simulation results are shown to validate the proposed approach.