To provide a method for efficiently and safely purifying environment contaminated in a wide range by radioactive cesium with low concentration at low cost.

In a method for purifying environment contaminated by radioactive cesium, the radioactive cesium in the environment is adsorbed by a bacterial cell of a Rhodobacter sphaeroides SSI strain (FERM P-21462), and the bacterial cell which adsorbs the radioactive cesium is collected from the inside of the environment. It is preferable to use a bacterial cell fixed carrier obtained by fixing the bacterial cell of the Rhodobacter sphaeroides SSI strain to a porous carrier in order to facilitate collection.