<p>A water supplying device (1) is provided with a water volume regulating unit (14) for changing the volume of water to be returned to a tank (11) through a return pipe (13) from a common pipe (2), and a control unit (15) for controlling a common pump unit (12) and the water volume regulating unit (14). The control unit (15) is configured so that the volume of water to be returned to the tank (11) from the common pipe (2) is controlled on the basis of the volume of water set to be supplied to an agricultural green house (8) to which water is to be supplied.</p>
