PURPOSE: To provide so that all the balls at respective points in a cylinder execute a powerful water purifying effect by producing swirling flow in the outer peripheral part in a cylindrical body contg. the balls for water purifying and activating elements and generating the rotating flow heading downward in the central part in the cylinder, thereby pushing back the balls tending to stagnate in the upper part of the cylinder downward and feeding the balls into the swirling flow again.

CONSTITUTION: An inlet filter plate 4 and an outlet filter plate 5 are respectively mounted on the upper and lower parts of the cylindrical body 1 joined with gaps at the top and bottom and the balls 6 consisting of ceramic materials are housed in the middle cavities of both filter plates. The inlet filter plate is partly provided with a slant hole 13 for passing the water and generating the swirling flow and a shaft rod 8 is mounted on the rear surface of the outlet filter plate. This shaft rod 8 is provide with inclined vanes 9 acting to push back a part of the swirling flow and the balls downward.