Ergosterol was crystallized from hexane solution by using a novel continuous column crystallizer equipped with a water feeding system. The water feeding system was used to control the water concentration of the crystallization solution at a ppm-level. Precipitates recovered from the bottom of the crystallizer were agglomerates that were a mixture of amorphous solid and monohydrate micro crystals. The water concentration of the crystallization solution played an important role for the size and the crystallinity of the precipitates. Large precipitates having a good filtration property were recovered when the water concentration of the solution was 162 ppm, namely when the mole ratio of water to ergosterol was 0.89.