A method of controlling a drinking water includes allowing a user to input a water discharge signal through an input lever, opening a first valve when a channel is closed by a water discharge valve to supply drinking water to a mixing tank, when the amount of drinking water supplied to the mixing tank reaches a first predetermined amount, opening a second valve to supply minerals to the mixing tank, and, when the amount of drinking water supplied to the mixing tank reaches a second predetermined amount, opening the water discharge valve to discharge mineral water to the outside through a spout.