C30B7/02

Refining method

A refining method according to the present invention is a refining method for crystallizing a compound with at least one crystal form, including: setting, as a target wavelength, a specific infrared wavelength at which a specific crystal form precipitates from a solution of the compound dissolved in a solvent; and using an infrared radiation apparatus capable of emitting infrared radiation including the target wavelength to evaporate the solvent and precipitate the specific crystal form while irradiating the solution with infrared radiation including the target wavelength. The specific infrared wavelength is preferably set as the target wavelength based on an infrared absorption spectrum of the crystal form and the dissolution rate of the compound in the solvent.