A magnetotactic bacterium contains magnetite (Fe₃O₄)p articles in its body and can swim toward the North Pole along geomagnetic field lines in the northern hemisphere. Using magnetotactic bacteria, we tried to observe the magnetic flux that was generated from magnetic materials. In our experiment, it became obvious that the magnetotactic bacteria distributed on the sample surface could be used to distinguish the magnetic south or north pole on the sample. We visualized the bacteria trajectory in order to obtain a two-dimensional image of the magnetic field strayed from magnetic materials.