NOVELTY - The system has a generation unit (HX7) that heats a coolant liquid by exchanging heat with a natural heat medium (SW) flowing through a natural heat-medium circuit (3). A heating unit (HX8) heats a natural gas (NG) supplied to an expansion turbine (NGT) in a natural gas direct expansion circuit (1) by exchanging heat with a heat medium (HW). A coolant steam heating unit (HX9) heats a coolant steam (RG) supplied to an expansion turbine (RGT) in a Rankine-cycle circuit (2) by exchanging heat with heating heat medium flowing through a heating heat-medium circuit (4).    USE - System for generating electric power by cooling-heat of liquefied natural gas using seawater, river water, hot-spring water, and geothermal water as heat source.    ADVANTAGE - The coolant steam heating unit heats the coolant steam supplied to the coolant steam expansion turbine in Rankine-cycle circuit by exchanging the heat with heating heat medium flowing through heating heat-medium circuit so that the coolant liquid supplied with the coolant liquid pump is heated in coolant steam generation unit by exchanging heat with a natural heat medium and vaporizing to coolant steam in Rankine-cycle circuit and is supplied to coolant steam expansion turbine after the coolant steam is heated in coolant steam heating unit by heat exchange with heating heat medium. Thus, only one of natural heat medium and heating heat medium is utilized as heat source to more highly maintain the pressure of coolant steam supplied to coolant steam expansion turbine so as to increase power generation output with the expansion turbine while ensuring stable supply of natural heat medium in natural heat-medium circuit even when supply of heating heat medium in heating heat-medium circuit is stopped with the stop of heat generation apparatus. Hence, the heat of liquefied natural gas is cooled and efficiently utilized while ensuring stability and safe operation.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic block diagram of the liquefied natural gas cooling-heat electric power generation system. (Drawing includes non-English language text)    Natural gas direct expansion circuit (1)    Rankine-cycle circuit (2)    Natural heat-medium circuit (3)    Heating heat-medium circuit (4)    Heat medium (HW)    Coolant steam generation unit (HX7)    Natural gas heating unit (HX8)    Coolant steam heating unit (HX9)    Natural gas (NG)    Natural gas expansion turbine (NGT)    Coolant steam (RG)    Coolant steam expansion turbine (RGT)    Natural heat medium (SW)