Abstract: A condenser-evaporator is constituted in such a way that first fluid chambers and second fluid chambers are alternately formed by multiple vertical partitions and a liquid in the first fluid chambers exchange heat with a fluid in the second fluid chambers, characterized in that a plurality of heat exchanger plates are arranged in multiple stages in the first fluid chambers to form a liquid passage having one end open, a plurality of liquid reservoirs communicating with the liquid passage and having a top open are provided in multiple stages on a side of the other end of the liquid passage, and a liquid is introduced in the liquid passage for heat exchange while being supplied to the liquid reservoir in each stage. Accordingly, the depth of the liquid is shallow so as to prevent a boiling point elevation due to the liquid head pressure, thus improving the efficiency of the condenser-evaporator.