PURPOSE: To automatically adjust the buoyancy of the support floating body which supports the said structure, horizontally maintain it at all times, and quickly remove the distortion caused by moving load by controlling the liquid and compressed air which enter into the structure in accordance with the distortion caused by moving load.

CONSTITUTION: When there occurs distortion in the floating body structure 1 due to the moving load of large vehicles, the distortion detecting photo detector 10 installed in it rises or falls. The laser beam 8 is received from the central photo detecting section 11 to the lower or upper photo detecting section 11. This permits the distortion detecting electrical signals to be sent to the air pressure adjusting solenoid valve 19 through the amplifier 12. When this solenoid valve 19 is actuated, air is sent to the support floating body 3 from the compressor 18 or compressed air is discharged from the air exhaust pipe 23. Sea water is introduced into the support floating body 3 and adjusts the buoyancy of the support floating body 3.