PURPOSE: To detect pressure difference in a cold plate directly with regard to a refrigerant-flow monitoring structure, which checks whether a constant amount of the refrigerant flows in the cold plate for cooling heated parts especially formed on a substrate.

CONSTITUTION: In a refrigerant-flow monitoring structure for monitoring the flow of refrigerant, which is supplied on a cold plate 2, a supplied-refrigerant path 7 and a discharge-refrigerant path 8 in the cold plate 2 are connected. A pressure identifying part 5, which reacts with the pressure difference of the refrigerant flowing through the supplied-refrigerant path 7 and the discharge- refrigerant path 8 in the cold plate 2, is provided. The flow of the refrigerant is monitored by detecting the pressure difference of the refrigerant in the cold plate.