According to one embodiment, a method for removing carbon dioxide in an exhaust gas utilizing seawater includes: blowing ammonia into seawater to produce ammonia-saturated seawater; contacting an exhaust gas under a state of non-heat with the ammonia-saturated seawater so that carbon dioxide in the exhaust gas is absorbed in the ammonia-saturated seawater; and splaying a solution containing sodium hydrogen carbonate and ammonium chloride which are produced through absorption of the carbon dioxide by the ammonia-saturated seawater utilizing pressure of the exhaust gas while cooling the solution utilizing heat of evaporation of a solvent of the solution so as to settle out and recover the sodium hydrogen carbonate and the ammonium chloride.