In order to reduce the number of structural components, the size and the cost of an electrolyzed water producing apparatus, an electrolyzed water producing apparatus is equipped with a system in which the start and stop of the operation of an electrolyzer cell in the apparatus is controlled in accordance with the open/close operation of a water feed valve interposed in a raw water feed conduit for feeding raw water to the electrolyzer cell. An electrolyzed water producing apparatus comprises: an electrolyzer cell subdivided into an electrolyzing anode chamber and an electrolyzing cathode chamber with a partition membrane; a raw water feed conduit for feeding raw water from a water supply source to the electrolyzing chambers of the electrolyzer cell; a water feed valve interposed in the raw water feed conduit; a brine feed conduit connected to the raw water feed conduit; a brine feed pump interposed in the way of the brine feed conduit; a control means for start/stop controlling the operation of the electrolyzer cell in accordance with on/off condition of the water feed valve and for controlling the operation of the brine feed pump in order to regulate the concentration of water to be electrolyzed as fed to the electrolyzer cell; a diluting water feed conduit bifurcated from the raw water feed conduit at a point downstream of the water feed valve; and a communicating conduit connecting one of the electrolyzing chambers to the diluting water feed conduit for diluting electrolyzed water discharging from the one of the electrolyzing chambers with the raw water diverging from the raw water feed conduit and flowing through the diluting water feed conduit when the electrolyzer cell is in operation, wherein a percentage of the raw water diverging from the raw water feed conduit into the diluting water feed conduit is regulated to accordingly regulate a concentration of the diluted electrolyzed water to be taken out.