PURPOSE: To enable power generation effectively utilizing a sea bottom flow by providing a rotary shaft provided with a large number of rotary vanes and connecting the rotary shaft to a generator to submerge the entire part of the generating system.

CONSTITUTION: An outer tube 1A forms an air chamber, and an inner tube 1B forms a sea bottom passage. This passage is provided at the central part with a generator chamber 3. Rotary shafts 5 and 5' provided with a large number of rotaty vanes 4 and 4' are mounted along the length direction on passages (a) and (b) at both side ends around the generator chamber 3. Air with in the above outer tube 1A is released, and the outer tube 1A is submerged in the sea bottom and the rotary vanes 4 and 4' are rotated thereby to drive the generator.