To prepare a mineral supplementing agent capable of commonly used for a seasoning liquid, a supplement, a cosmetic, an oral cavity washing liquid, a plant growth promoting agent and the like, by using common materials and a common preparation method. A method of preparing a mineral supplementing agent capable of being administered to a human body or a plant is provided. The method includes a first charging step, a second charging step, a third charging step, a fourth charging step, and an extraction step. The first charging step charges a vessel with part of a prescribed amount of vinegar. The second charging step charges the vessel, which has been charged with the vinegar, with at least one of garlic, instant coffee, vinegar, and a fruit. The third charging step charges the vessel, which has been subjected to the second charging step, with at least one of a particulate grain hull, a charred product thereof, and a calcined ash thereof, and mixing the contents of the vessel. The fourth charging step adds the rest of the prescribed amount of vinegar to the vessel which has been subjected to the third charging step, while stirring the contents of the vessel concurrently with the addition. The extraction step separates a liquid component and a solid component in the vessel, after the fourth charging step, and extracts the separated liquid component as a mineral solution.
