PURPOSE: To cope with the difference in the state of city waters such as the dust content and the strength of the bleaching powder odor or with the difference in taste of users to minimize the bleaching powder odor, etc.

CONSTITUTION: Three cartridges 5 to 7 of the same shape are detachably housed in a treating device main body consisting of a main case 1 and an upper case 3. The cartridges are connected to one another so that the supplied city water ia allowed to flow in series. The cartridge contains activated carbon or a filter medium such as a hollow-fiber membrane. The cartridges contg. an appropriate filter medium in accordance with the state of city water are housed in the main body in appropriate order.