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 r
