It is an object of the present invention to provide a method for improving the solubility of a poorly-soluble substance, which is capable of increasing the solubility of substantially all poorly-soluble substances. This is a method comprising coating the surface of a poorly-soluble substance particle with microparticles of a calcium compound such as calcium phosphate or calcium carbonate, and at least one selected from a pH adjuster and a surfactant, by applying mechanical energy thereto.
