To surely operate a water treating apparatus in spite of fluctuation of water pressure and water flow rate by forcibly operating a check valve of a concentrated flow path control unit of this apparatus.

The concentrated flow path control unit D consists of the first pipeline d1, the second pipeline d2 and the third pipeline d3 which is communicated with one end of the pipeline d2. The first check valve to be induced by a magnetic induction ring 40 is provided in the pipeline 1 at the position to cross the pipeline 2 so that a ball 21 is forcibly kept in check at the position of the valve port 22 by applying the prescribed electric current to the ring 40. In the same manner, the second check valve to be induced by another magnetic induction ring 41 is provided in the pipeline d3. Switches S1, S2 are provided at one end of the pipeline d3 for starting/stopping an electrolytic cell, reversing the polarity and supplying operational power to the ring 40 or 41 by operating respective switches. When water pressure is lower than the prescribed pressure and is fluctuated, a valve port 31 is forcibly kept in check by applying the prescribed currents to the rings 40, 41.