Provided is a method for stably obtaining a product. The present invention relate to a tank for use in a purification apparatus, the tank being: at least one of a crystallization tank that forms a slurry containing crystals of a compound or a ripening tank that is capable of keeping crystals of a compound suspended therein, the tank including a nozzle for feeding a compound-containing solution or a slurry containing crystals of a compound into the tank while the solution or slurry is brought into contact with an inner wall surface of the tank; and a heating mechanism for heating an area of the inner wall surface with which the compound-containing solution or the slurry containing crystals of a compound is to be brought into contact.