A water purifier that includes: a water storage tank that includes an interior area and a first opening to the interior area; a cover unit that is configured to cover the first opening and that includes: a frame body that includes a second opening, and a water storage tank cover that is coupled to the frame body and that is configured to rotate about an axis such that the water storage tank cover opens or closes the second opening; a sterilizer that is configured to sterilize water in the water storage tank; a switching module that is configured to control electric power supply to the sterilizer; and an operation member that is configured to control the switching module based on the water storage tank cover being opened or closed is disclosed.