Pure stainless steel (SUS 316L) powders with both a nano-grain and micro-structure were prepared using a mechanical milling process. The bimodal microstructure consists of a nano-grain with a size of 50 nm in the surface region and microstructure in the core of the particle. The nano-grain with a bcc structure at the surface and the microstructure of fcc in the core of the particles were prepared by milling at 150rpm for 9h, and those compositions were 14.39% for the nano structure and 85.61% for the micro structure, respectively. Spark plasma sintering (SPS) was carried out for the compaction of the powders. The compacts forming powders with a bi-modal structure have a mesoscopic structure.