In the production process of an SOI substrate using a hydrogen ion implantation method, a process is provided for cleaning the substrate which can prevent formation of voids when bonding substrates and formation of blistering after exfoliation. In the process for cleaning, cleaning of the substrate is performed before performing hydrogen ion implantation. As the cleaning method, one or more of a combination selected from the group consisting of SC-1 cleaning, SC-1 cleaning+SC-2 cleaning, HF/O.sub.3 cleaning, and HF cleaning+O.sub.3 cleaning, can be used.