A total dissolved solid controlling apparatus comprising: a filtering unit including a deionizing filter removing dissolved solids from inflow raw water by an input current; and a control unit controlling the input current such that water discharged from the deionizing filter corresponds to target total dissolved solids, wherein the control unit comprises: a determiner determining total dissolved solids contained in raw water having flowed into the deionizing filter, by using an input current; and an input current determiner comparing the determined total dissolved solids with the target total dissolved solids, and determining an input current applied to the deionizing filter, based on the comparison results; an input current supplier applying a predetermined fixed voltage to the deionizing filter, and supplying the input current to the deionizing filter by pulse width modulation; and a flow rate sensor measuring a flow rate of raw water flowing into the deionizing filter, wherein the input current determiner determines the input current applied to the deionizing filter, based on the comparison results of the determined total dissolved solids and the target total dissolved solids, and the flow rate of raw water measured by the flow rate sensor. a filtering unit including a deionizing filter removing dissolved solids from inflow raw water by an input current; and a control unit controlling the input current such that water discharged from the deionizing filter corresponds to target total dissolved solids, wherein the control unit comprises: a determiner determining total dissolved solids contained in raw water having flowed into the deionizing filter, by using an input current; and an input current determiner comparing the determined total dissolved solids with the target total dissolved solids, and determining an input current applied to the deionizing filter, based on the comparison results; an input current supplier applying a predetermined fixed voltage to the deionizing filter, and supplying the input current to the deionizing filter by pulse width modulation; and a flow rate sensor measuring a flow rate of raw water flowing into the deionizing filter, wherein the input current determiner determines the input current applied to the deionizing filter, based on the comparison results of the determined total dissolved solids and the target total dissolved solids, and the flow rate of raw water measured by the flow rate sensor. a determiner determining total dissolved solids contained in raw water having flowed into the deionizing filter, by using an input current; and an input current determiner comparing the determined total dissolved solids with the target total dissolved solids, and determining an input current applied to the deionizing filter, based on the comparison results; an input current supplier applying a predetermined fixed voltage to the deionizing filter, and supplying the input current to the deionizing filter by pulse width modulation; and a flow rate sensor measuring a flow rate of raw water flowing into the deionizing filter, wherein the input current determiner determines the input current applied to the deionizing filter, based on the comparison results of the determined total dissolved solids and the target total dissolved solids, and the flow rate of raw water measured by the flow rate sensor.