PURPOSE: To constitute the device so that necessary driving power of a compressor is curtailed and carbon dioxide can be separated efficiently, and also, at a low operation cost by an easy and simple constitution.

CONSTITUTION: In the carbon dioxide separating device for separating carbon dioxide from exhaust gas containing dioxide, this device is provided with a water channel piping for leading in water or sea water 1, a liquid gas heat exchanger 3 which is provided on the upstream side of the water channel piping, and performs heat exchange for liquid natural gas, and a gas leading-in piping for leading in exhaust gas, and a seawater heat exchanger 6 which is provided on the downstream side of the water channel piping, and performs heat exchange for sea water, and a carbon dioxide collecting piping 7 for collecting carbon dioxide.