By efficiently lowering a water temperature of a sea surface to thereby suppress an evaporation of a water vapor from the sea surface by lowering the water temperature of the sea surface, a generation of an atmospheric depression is prevented or its strength is weakened. Further, by suppressing a rise of the sea surface temperature, a generation of a red tide or a blue tide is prevented or reduced. As an apparatus for lowering the water temperature of the sea surface, it is constituted such that a pipe for feeding a water is installed in a sea, a suction port of the pipe is disposed in a cold water zone whose temperature is lower than the water temperature of an aim sea surface, an injection port of the pipe is disposed in a required position below the sea surface, and a pump is connected to the pipe in order to suck a cold water from the suction port and inject it from the injection port to thereby supply it below the sea surface in a region of the aim sea surface, thereby mixing it with a warm water of higher temperature.