There is provided a method of producing a product inorganic compound including: a step A in which a raw material inorganic compound having a volume of 10 -13 m 3 or more is immersed in an electrolyte aqueous solution or an electrolyte suspension a step B1 in which anions in the raw material inorganic compound are exchanged with anions in the electrolyte aqueous solution or the electrolyte suspension a step B2 in which cations in the raw material inorganic compound are exchanged with cations in the electrolyte aqueous solution or the electrolyte suspension or a step B3 in which a component (provided that it excludes water, hydrogen, and oxygen) in the electrolyte aqueous solution or the electrolyte suspension that is not included in the raw material inorganic compound is made to be included in the raw material inorganic compound and a step C in which a product inorganic compound having a volume of 10 -13 m 3 or more is obtained from the raw material inorganic compound, wherein the raw material inorganic compound has a solubility that is greater than 0 and 5 or less with respect to distilled water or the electrolyte aqueous solution at 20 °C, and wherein, in the electrolyte aqueous solution or the electrolyte suspension in which the raw material inorganic compound is immersed, at least, elements other than hydrogen and oxygen, which are included in the product inorganic compound but not included in the raw material inorganic compound are included (provided that it excludes a production method in which an apatite without pores with a diameter of 20 µm or more and an aspect ratio of 2 or more is produced from at least one selected from the group consisting of calcium sulfate dihydrate, ±-type tricalcium phosphate, and calcium carbonate, a production method in which calcium sulfate is immersed in an ammonia or alkali metal hydroxide-containing aqueous solution, carbon dioxide is introduced into the aqueous solution, and calcium carbonate without pores with a diameter
