An ion removal system comprising: an electrolysis device configured to generate alkaline water and acid water by electrolysis; a hard water flow path connected to the electrolysis device to supply the electrolysis device with hard water; a batch treatment tank provided in the hard water flow path to store the hard water; a first flow path and a second flow path through which the alkaline water and the acid water generated by the electrolysis device can alternately flow; a return flow path connected to the batch treatment tank to return the alkaline water or the acid water generated by the electrolysis device to the batch treatment tank, wherein the return flow path includes a first return flow path connected from the first flow path to the batch treatment tank, and a second return flow path connected from the second flow path to the batch treatment tank; a fine bubble generation device configured to adsorb and remove metal ions in water by the fine bubbles generated, wherein the fine bubble generation device includes a fine bubble generation device configured to generate fine bubbles in a circulation flow path including the batch treatment tank, the electrolysis device, the first flow path, and the first return flow path, and a fine bubble generation device configured to generate fine bubbles in a circulation flow path including the batch treatment tank, the electrolysis device, the second flow path, and the second return flow path; and a controller configured to alternately perform a first mode and a second mode, wherein, in the first mode, the alkaline water is allowed to flow through the first flow path and the acid water is allowed to flow through the second flow path, and, in the second mode, the acid water is allowed to flow through the first flow path and the alkaline water is allowed to flow through the second flow path. an electrolysis device configured to generate alkaline water and acid water by electrolysis; a hard water flow path connected to the electrolysis device to supply the electrolysis device with hard water; a batch treatment tank provided in the hard water flow path to store the hard water; a first flow path and a second flow path through which the alkaline water and the acid water generated by the electrolysis device can alternately flow; a return flow path connected to the batch treatment tank to return the alkaline water or the acid water generated by the electrolysis device to the batch treatment tank, wherein the return flow path includes a first return flow path connected from the first flow path to the batch treatment tank, and a second return flow path connected from the second flow path to the batch treatment tank; a fine bubble generation device configured to adsorb and remove metal ions in water by the fine bubbles generated, wherein the fine bubble generation device includes a fine bubble generation device configured to generate fine bubbles in a circulation flow path including the batch treatment tank, the electrolysis device, the first flow path, and the first return flow path, and a fine bubble generation device configured to generate fine bubbles in a circulation flow path including the batch treatment tank, the electrolysis device, the second flow path, and the second return flow path; and a controller configured to alternately perform a first mode and a second mode, wherein, in the first mode, the alkaline water is allowed to flow through the first flow path and the acid water is allowed to flow through the second flow path, and, in the second mode, the acid water is allowed to flow through the first flow path and the alkaline water is allowed to flow through the second flow path.