To improve the regeneration efficiency of an adsorption section without increasing the water supply amount.

When bacteria and the like are removed from tap water and purified drinking water is supplied, the tap water flows into a purified water feed means 12 and bacteria and the like are removed by an adsorption section 10a of a water purifying instrument 10 and supplied to a tap 12a. On the other hand, when the water purifying operation is carried out for a long time, fouls adhere to the adsorption section 10a and it is necessary to remove the fouls from the adsorption section 10a. When the adsorption section 10a is regenerated, hot water is circulated between the hot water preparation instrument 11 and the adsorption section 10a through a hot water circulation piping 13a. As circulating water can be reheated by the hot water preparation instrument 11 during the circulation, the temperature of the adsorption section 10a can be kept suitable for regeneration, and also the hot water is circulated continuously in the adsorption section 10a to clean the adsortion section 10a securely.