A pH-adjusted water production device has a configuration in which a platinum group metal support resin column, a membrane-type degassing device, and a gas dissolving membrane device are provided on an ultra-pure water supply line, and a pH-adjuster injection device is provided between the platinum group metal support resin column and the membrane-type degassing device. An inert gas source is connected to the gas phase side of the membrane-type degassing device while an inert gas source is connected also on the gas phase side of the gas dissolving membrane device, and a discharge line communicates with the gas dissolving membrane device.