An ion removing system comprising: an ion removing apparatus that comprises a hard water storage part storing hard water and a fine bubble generating part which is configured to generate and supply fine bubbles to the hard water storage part, causing the fine bubbles to adsorb metal ions in the hard water in the hard water storage part to remove the metal ions from the hard water, a primary-side flow path connected to the ion removing apparatus which is configured to supply the hard water to the ion removing apparatus, a separating apparatus connected to the ion removing apparatus which is configured to separate crystals of a metal component deposited by crystallizing the metal ions removed from the hard water by the ion removing apparatus, a solubilizer supply part which is configured to supply a solubilizer for dissolving the crystals to an upstream side in a flow direction of the hard water relative to the separating apparatus, and a secondary-side flow path connected to the separating apparatus which is configured to take out, from the separating apparatus, treated water obtained by separating the crystals, wherein the primary-side flow path is provided with a supply-side backflow prevention mechanism, the fine bubbles comprise bubbles having a diameter of 100 μm or less in a proportion of 90% or more, the fine bubble generating part is configured to generate the fine bubbles with a mixture gas of a first gas and a second gas, the mixture gas is the ion removal gas for removing metal ions in the hard water, the first gas is a hydroxyl ion-donating gas configured to react with water to donate hydroxyl ions, the second gas has a slower solution velocity than that of the first gas, the separating apparatus is a cyclone-type centrifugal separating apparatus having a tapered inner circumferential surface with a diameter decreasing downward which is configured to cause the hard water to spirally flow downward along the inner circumferential surface so that the crystals of the metal component are separated, the solubilizer supply part is configured to supply the dissolution gas for dissolving the crystals as a solubilizer to the fine bubble generating part, wherein the dissolution gas is carbon dioxide, hydrogen sulfide, or hydrogen chloride, which is a gas producing hydrogen ions when dissolved in water, and wherein the fine bubble generating part is provided with a gas switching mechanism which is configured to supply either the ion removal gas or the dissolution gas. an ion removing apparatus that comprises a hard water storage part storing hard water and a fine bubble generating part which is configured to generate and supply fine bubbles to the hard water storage part, causing the fine bubbles to adsorb metal ions in the hard water in the hard water storage part to remove the metal ions from the hard water, a primary-side flow path connected to the ion removing apparatus which is configured to supply the hard water to the ion removing apparatus, a separating apparatus connected to the ion removing apparatus which is configured to separate crystals of a metal component deposited by crystallizing the metal ions removed from the hard water by the ion removing apparatus, a solubilizer supply part which is configured to supply a solubilizer for dissolving the crystals to an upstream side in a flow direction of the hard water relative to the separating apparatus, and a secondary-side flow path connected to the separating apparatus which is configured to take out, from the separating apparatus, treated water obtained by separating the crystals, wherein the primary-side flow path is provided with a supply-side backflow prevention mechanism, the fine bubbles comprise bubbles having a diameter of 100 μm or less in a proportion of 90% or more, the fine bubble generating part is configured to generate the fine bubbles with a mixture gas of a first gas and a second gas, the mixture gas is the ion removal gas for removing metal ions in the hard water, the first gas is a hydroxyl ion-donating gas configured to react with water to donate hydroxyl ions, the second gas has a slower solution velocity than that of the first gas, the separating apparatus is a cyclone-type centrifugal separating apparatus having a tapered inner circumferential surface with a diameter decreasing downward which is configured to cause the hard water to spirally flow downward along the inner circumferential surface so that the crystals of the metal component are separated, the solubilizer supply part is configured to supply the dissolution gas for dissolving the crystals as a solubilizer to the fine bubble generating part, wherein the dissolution gas is carbon dioxide, hydrogen sulfide, or hydrogen chloride, which is a gas producing hydrogen ions when dissolved in water, and wherein the fine bubble generating part is provided with a gas switching mechanism which is configured to supply either the ion removal gas or the dissolution gas.