To provide a crystallizer continuously operable, high in crystal production efficiency and obtaining fine and uniform crystals.

The crystallizer includes a cylindrical container 2; a heat transfer cylinder body 4 provided in the container 2 and rotated; a fixed shaft tube 6 provided at the center part in the heat transfer cylinder body 4; and fixed blades 7 fixed to the outer peripheral surface of the shaft tube 6 and approaching or coming in sliding contact with the inner peripheral surface of the heat transfer cylinder body 4 to strip off laminar films. A first passage 11a of a heat medium is formed in the heat transfer cylinder body 4, and a second passage 11b of raw material liquid is formed between the outer peripheral surface of the heat transfer cylinder body 4 and the inner peripheral surface of the container 2. The bottom 2a of the container 2 is provided with a crystal outflow tube.