The buffing process used in the repair polishing of an automotive body surface is carried out manually using skilled workers based on their own experience. However, the number of skilled workers available in the workforce is decreasing owing to the aging population. In addition, the surface quality after the buffing process has been applied is dependent on the proficiency level of the polishing worker. Therefore, an automation technology for the buffing process is required. In our previous research, we developed a polishing machine with a 5-axis serial-parallel mechanism, and extracted data on the tool trajectory, tool posture, and polishing force from a skilled worker. In addition, a method for simultaneously controlling the tool posture and polishing force on a curved surface was developed. The polishing machine successfully replicates a skilled buffing process on not only flat surfaces but also curved surfaces without applying a teaching-playback method, CAD data, or external sensors. This paper analyzes the proposed control method from the perspective of posture control, and verifies the utility experimentally on a semispherical surface.