A splash suppressing device for a water tank is provided with a housing (3) mounted inside a water tank, having a cavity therein, having an opening in a portion of the bottom side thereof which is submerged under water in the water tank, and having a closed upper side a fixing member (15) for fixing the housing (3) to the inner wall of the water tank an air stone (5) mounted in the cavity of the housing a connecting section (8) provided to a part of the housing and connected to an air tube (7) from an external air pump (10) and an air introducing path (9) for interconnecting the connecting section (8) and the air stone (5) to allow flow of gas. The air introducing path (9) can be easily replaced.
