PURPOSE: To manufacture easily mineral water having minerals eluted sufficiently, by putting natural porous stones in a cylindrical container in the center of a water tank and by circulating water by an underwater pump.

CONSTITUTION: In the center of the water tank having opening part 1 at the upper, cylindrical container 2 is provided and in the container, natural porous stones such as granitic stones are contained. Underwater pump 3 at the bottom part of cylindrical container 2 sucks water from the water tank bottom part and circulates the water to the upper in the cylinder. Then, since the water circulates in a water- activating filter device, mineral water having minerals eluted sufficiently is obtained and the replacement and washing of the natural porous stones and washing in the device are facilitated.