To understand characteristics of biogeochemical corrosion for the metal canisters that usually contain the radioactive wastes for a long-term period below the ground, some metal materials consisting of cast iron and copper were reacted for 3 months with D. desulfuricans, a sulfate-reducing bacterium, under a reducing condition. During the experiment, concentrations of dissolved metal ions were periodically measured, and then metal specimen and surface secondary products were examined using the electron microscopy to know the chemical and mineralogical changes of the original metal samples. The metal corrosion was not noticeable at the absence of D. desulfuricans, but it was relatively greater at the presence of the bacterium. In our experiment, darkish metal sulfides such as mackinawite and copper sulfide were the final products of biogeochemical metal corrosion, and they were easily scaled off the original specimen and suspended as colloids. For the copper specimen, in particular, there appeared an accelerated corrosion of copper in the presence of dissolved iron and bacteria in solution, probably due to a weakening of copper-copper binding caused by a growth of other phase, iron sulfide, on the copper surface.