PROBLEM TO BE SOLVED: To provide a farmland soil decontamination method, utilizing an organic acid and a filamentous bacterium/actinomycete biofilm, which breeds filamentous bacteria, actinomycetes, etc., in an organic acid solution and extracts cesium from soil to decontaminate farm land.SOLUTION: A farmland soil decontamination method utilizing an organic acid and a filamentous bacterium/actinomycete biofilm includes: forming the biofilm consisting principally of filamentous bacteria, actinomycetes, etc., on a soil surface by impregnating soil contaminated with radioactive cesium with one of 0.1-50.0%, preferably, 0.1-10.0% lactic acid, citric acid, malic acid, tartaric acid, acetic acid, gluconic acid, oxalic acid, fumaric acid, succinic acid, mugineic acid, and glycolic acid, or a solution of a mixture thereof; and peeling the biofilm off so as to remove the cesium that plants easily absorb.
