To provide a crystallizer with a simple structure which exhibits high classification performance in crystallization.

A rotary blade means 5 for generating a swirl flow in a raw material liquid of suspended slurry in a vessel 2 along an inner peripheral surface of the vessel 2 is provided in a center part of an upper part in the vertical vessel 2 having a classification leg 3 on a bottom part 2b, and a liquid flow direction changing means 6 for making the raw material liquid flow upward in the center part of the vessel 2 is provided in the center part of a bottom surface of the vessel. The liquid flow direction changing means 6 is constituted of a strip-shaped baffle 6a radially disposed on the bottom surface.