The selective removal of low-concentration heavy metal ions from heavy-metal-contaminated water was investigated using the activity or sulfate-reducing bacteria (SRB) immobilized on a fibrous slag (FS), which was employed as a both biocarrier and a fine particle collector medium. An upflow-type bioreactor composed of an FS-packed column, where SRB were immobilized at a lower part, was used. In this process, sulfate ions in the liquid are biologically reduced to sulfide ions, which react with metal ionic species to produce ultrafine metal sulfide particles. Subsequently, formed particles adhere onto the FS surface in the upper part of the reactor, thereby accumulating heavy metal ions as their sulfide precipitates. Five different organic compounds were evaluated, and as a result, lactic acid was found to serve as the most suitable electron donor for SRB in this system. In the continuous treatment of water contaminated with several heavy metal ions (Cd²⁺, Cu²⁺, Ni²⁺, Zn²⁺, and Mn²⁺), almost complete removal was attained over an 80-day operation period, except for Mn²⁺ having a relatively high solubility product constant. Heavy metal sulfide precipitates gradually accumulated on an FS bed. These experimental results indicate that the proposed bioreactor, which is the sulfate-reducing bioreactor with a fibrous slag carrier (SRB-FS), enables the efficient recovery of heavy metal ions from heavy-metal-contaminated water.