We proposed a novel bioremediation method, bioremediation by the self-immobilization system (BSIS), for application to treat pollution of soil spreading over a wide area. In this method, cells are immobilized by spontaneous formation of aggregates and retained in soil. We selected B. subtilis IFO3335 strain, which secretes viscous filaments and forms strong aggregates, as one of strains suitable for this bioremediation method based on self-immobilization, and studied their behavior in soil. These cells could be retained at a shallow layer under soil for a long period.