The application of sliding mode control with Luenberger-style observer for robot manipulator is concerned in this paper. The proposed approach rely only on joint position messages without velocity measurement, also the motor dynamics is taken into consideration. The system is separated as two subsystems named as the robot joint part and the motor driven part. We first apply a novel Luenberger-style observer to estimate the joint velocity information, which overcome the disadvantage of sliding mode control that all output states are needed. Then, the trajectory tracking controller using the observer is developed via backstepping design method. Stability of the system has been strictly proved by Lyapunov theory, which is shown that the tracking errors converge to zero asymptotically. Further simulation results on a two-link robot manipulator are presented to validate the analysis..