PURPOSE: To easily set a load and to easily change the temporarily set load by outputting a load setting signal showing plural load setting states to a power station model based on the operation of a load setting manipulator.

CONSTITUTION: When evaporating LNG and outputting natural gas, a plant controller 3 simulatively controls the quantity of gas to be sent out corresponding to the consumption of natural gas at a power station by controlling the flow rate of LNG to flow into each evaporator. The power station model simulates the operating state of the power station such as the load state of the power station and the number of boilers to be operated based on the load setting signal outputted corresponding to the setting of various load setting buttons provided on a load setting panel 1 and a power station control signal outputted from the plant controller 3. Then, the load state signal provided as a result is outputted to a process simulation computer 4 and the operating state signal is outputted to the plant controller 3. Therefore, plural load setting patterns can be set based on the operations of load setting buttons.