PROBLEM TO BE SOLVED: To provide a bacterium supply module for supplying bacteria of a specified quantity without any trouble into the water.SOLUTION: A bacterium supply module 1 comprises: a bubble generation body 11 made of a porous material having continuous pores a bacterium carried on the bubble generation body 11 and an air introduction part 12 for introducing air into the bubble generation body 11. The bacterium is one belonging to the genus Bacillus.SELECTED DRAWING: Figure 1