WATER PURIFIER

PROBLEM TO BE SOLVED: To control to optimize washing of a filter medium in accordance with a change with time and a ambient change of the filter medium. SOLUTION: This device is provided with the filter medium, a filter container for housing the filter medium, a heating means for raising the temperature of the filter medium housed in the filter medium container, an inflow pipe for introducing water into the filter medium container, a discharge pipe for discharging water from the filter medium container, a temperature detecting means 8 for detecting the temperature in the filter medium container, and a memory element for storing the heating time. When the heating means is controlled of the heating time, the heating time is changed based on the information of the temperature detecting means 8 at the previous heating time.