Abstract: Disclosed is a water purifier that includes a deionization device for purifying water with electric power, and a controller electrically connected to the deionization. The deionization device includes a housing and a plurality of electric filters arranged in a plurality of isolation rooms formed in the housing. The controller operates the plurality of electric filters by dividing the plurality of electric filters into a plurality of electric adsorption filters which adsorb ionic materials and at least one electric resting filter which remains in a standby state during a water purification operation, and restart the water purification operation or perform a recycling operation to recycle the plurality of electric filters, depending on whether a restart command for the water purification operation is input within a preset waiting time from a point in time when the water purification operation is stopped.