In this study, the trajectory planning method of the knife position of a slitter robot is proposed, and the experimental and numerical simulation results are demonstrated. The slitter robot consists of upper and lower knife driving mechanisms, and a knife driving mechanism was constructed with a worm gear, a ball screw and an alternating current (AC) motor. In the trajectory planning, first, the identification algorithm of the friction and the viscous damping is derived by using the equation of motion of the knife drive mechanism and the experimental results of the dynamic response with constant AC motor torque. Then, the trajectory planning algorithm of the knife position is presented, and a knife position control system is constructed. Furthermore, the experiments and numerical calculations have been carried out, and the usefulness of the present trajectory planning method is confirmed.