To effectively and securely check ballast water surface water by providing a float having an ejector inside to float on the surface of ballast water through a sounding pipe having plural holes continuously provided in a length direction in an outer circumference, and lifting the surfacewater by the ejector.

In a lifting device 1, a float 2 is provided to float on surface water W of ballast water L through a sounding pipe 37 having plural holes 37a continuously provided in a length direction in an outer circumference as a guide pipe. The surface water w gets into the sounding pipe 37 through the hole 37a. The float 2 is provided with an ejector 3 having a surface water inlet port 3b, and a compression air supply machine 5 is connected by a jet tube 4. In addition, it is connected to a storage part 7 by a discharge tube 6. Compression air is introduced from the compression air supply machine 5 to the ejector 3, and the surface water W invading into the sounding pipe 37 by action of the ejector is lifted to the storage part 7.