A water supply apparatus is provided to meet demands for energy saving by controlling the rotational speed of a pump (1), for example, so as to lower the rotational speed in the time zone when water is not used much while avoiding the time zone when water is used in large quantities. The water supply apparatus includes the pump (1) configured to pressurize and deliver water, a frequency converter configured to supply electric power to the pump (1) to operate the pump (1) at a variable speed, and a controller (15) configured to send operating signals to the frequency converter so as to operate the pump (1) either at a first operation or at a second operation with less power consumption than the first operation. The controller (15) is configured to judge whether the operation of the pump (1) should be shifted from the first operation to the second operation based on an operational state of the pump (1).