The present invention provides a maintenance system for wind turbine equipment. The maintenance system includes a trolley support unit (130), a trolley (140), a pulley, a winch unit (150) and a door (160). The trolley support unit is provided in the nacelle so as to be movable in the longitudinal direction of the nacelle. The trolley is provided on the trolley support unit so as to be movable in the lateral direction of the nacelle. The pulley is rotatably installed in the trolley. The winch unit is connected to the pulley through a wire. The door is provided in the nacelle so that an element of the nacelle to be repaired is removed from or inserted into the nacelle through the door. Therefore, in the present invention, when maintenance or repair of an element in the nacelle is required, it can be conveniently conducted without using a separate crane.