An innovative planarization system named plasma fusion CMP was developed for aiming to establish a high-efficiency/high-quality polishing process of the hard-to-process materials. In this study, we applied this system to processing of diamond substrate instead of conventional CMP (Chemical Mechanical Polishing) process. We confirmed that stable atmospheric plasma was generated in our dynamic system, and the system worked well even though CMP slurry was applied into the system. In the processing experiments of diamond substrate, plasma fusion CMP achieved 667.7 nm/hr of processing rate while conventional CMP resulted in only 1.9 nm/hr. Furthermore, plasma fusion CMP showed the superior surface roughness reduction of the substrate to CMP.