To provide a wall component for fluid, capable of restraining air bubbles from growing and preventing contamination components from adhering or being deposited by avoiding adhesion of the air bubbles, and to provide an air bubble generating system and a filtering system capable of efficiently purifying fluid with minute air bubbles.

In an air generating device 4, the minute air bubbles are generated by taking hot water 2 in a bath tub 100, and forcing the outside air into before discharging the hot water, and the hot water including a large volume of minute air bubbles is discharged to the bottom of the bath tub via a discharge piping 5. While the minute air bubbles are moving upward inside the bath tub, the contamination components in the hot water are attached to the air bubbles and the air bubbles absorbing and adhering to the contamination components and bubbles are taken from the vicinity of the water surface and taken unto a filtering device 7 via an intake piping 6. The hot water of which contamination components have been filtered and removed is returned to the bath tub. At least on an inner surface of the discharge piping and the intake piping, hydrophilic coating exerting affinity for water is formed for preventing the air bubbles from adhesion. The discharge piping and the intake piping may be constituted by a hydrophilic material. In this case, it is sufficient to apply only reinforcing covering exerting durability and strength.