An apparatus (100, 101, 102) for producing carbonated water, the apparatus comprising: a gas cylinder in which a carbon dioxide gas is filled; a cold water storage unit in which cold water is stored; a producing tank defining a closed space in which the carbonated water is produced; a water supply passage connecting the cold water storage unit to the producing tank, the water supply passage comprising a water supply valve that is opened and closed to supply the cold water; a gas supply passage (400; 450) connecting the gas cylinder to the producing tank, the gas supply passage comprising a gas valve that is opened and closed to supply the carbon dioxide gas; a first relief valve provided in the gas supply passage (400; 450), the first relief valve being opened to discharge the carbon dioxide gas; a dispensing passage connecting the producing tank to a dispensing member for dispensing the carbonated water, the dispensing passage comprising a dispensing valve that is opened and closed to dispense the carbonated water; a second relief valve communicating with an upper portion of the producing tank, the second relief valve being opened to discharge air within the producing tank; and a controller controlling operations of the gas valve and the relief valves (420, 610), wherein the controller determines an opening time of the gas valve according to a concentration setting input of a user, wherein the controller controls the gas valve so that the gas valve is continuously opened until the carbonated water within the producing tank reaches a preset concentration, wherein the second relief valve has a preset pressure that is greater than the atmospheric pressure and less than that of the first relief valve, and when the carbon dioxide gas is continuously injected into the producing tank, the second relief valve is opened. a gas cylinder in which a carbon dioxide gas is filled; a cold water storage unit in which cold water is stored; a producing tank defining a closed space in which the carbonated water is produced; a water supply passage connecting the cold water storage unit to the producing tank, the water supply passage comprising a water supply valve that is opened and closed to supply the cold water; a gas supply passage (400; 450) connecting the gas cylinder to the producing tank, the gas supply passage comprising a gas valve that is opened and closed to supply the carbon dioxide gas; a first relief valve provided in the gas supply passage (400; 450), the first relief valve being opened to discharge the carbon dioxide gas; a dispensing passage connecting the producing tank to a dispensing member for dispensing the carbonated water, the dispensing passage comprising a dispensing valve that is opened and closed to dispense the carbonated water; a second relief valve communicating with an upper portion of the producing tank, the second relief valve being opened to discharge air within the producing tank; and a controller controlling operations of the gas valve and the relief valves (420, 610), wherein the controller determines an opening time of the gas valve according to a concentration setting input of a user, wherein the controller controls the gas valve so that the gas valve is continuously opened until the carbonated water within the producing tank reaches a preset concentration, wherein the second relief valve has a preset pressure that is greater than the atmospheric pressure and less than that of the first relief valve, and when the carbon dioxide gas is continuously injected into the producing tank, the second relief valve is opened.