To provide a crystallization method capable of reducing the amount of crystals bonded to the wall surface of a crystallization tank in a state difficult to recover and capable of being satisfied economically.

In the crystallization method for cooling a solution of a compound to crystallize the compound, the composition of the solution at the start time of cooling is set so that the differentiated value of a solubility curve in the composition becomes 10 g/°C or more and the concentration of the solution is not less than the concentration corresponding to the saturated solubility at the temperature at the start time of cooling and the crystal nuclei of the compound are contained in the solution excepting the wall surface part of the crystallization tank in which the solution is housed.