A water purifier is provided. The water purifier includes a purified water tank for storing purified water, a hot water tank including a heater for heating the purified water supplied from the purified water tank, a purified water supply pipe connecting the purified water tank and the hot water tank to supply the purified water of the purified water tank to the hot water tank, a purified water supply valve opening or closing the purified water supply pipe, a manipulation unit through which a user inputs an extraction amount of hot water, a memory unit for readably storing an opening time of the purified water supply pipe depending on an amount of purified water to be supplied to the hot water tank, and a control unit setting the extraction amount of hot water to the amount of purified water to be supplied to the hot water tank when the extraction amount of hot water is inputted through the manipulation unit, reading the opening time of the purified water supply pipe corresponding to the amount of purified water to be supplied to the hot water tank from the memory unit, and opening the purified water supply pipe during a specified opening time.