To provide a method for decomposing and treating a pollutant of persistency which influences an adverse effect on the environment by using a bacterial bed having a decomposition capacity of the pollutant.

In the case of filling a mixture 1 obtained by mixing polluted soil containing the pollutant with a bacterial bed of eatable bacteria or a waste bacterial bed into a drum can 2, a filling material 4 having air distribution properties such as glass wool is inserted between the mixture 1 and the drum can 2, An air introduction tube 5 for supplying air to the filling material 4 is disposed in a cover 3. Further, a filter 6 is fitted in the air introduction tube 5 and thereby harmful gas capable of being generated from the pollutant in the mixture 1 is prevented from being leaked to the outside air.