PURPOSE: To facilitate measurement of a load of a jack unit, by mounting a load gauge between a jack unit and a jack house through the medium of a buffer material and a spherical seat.

CONSTITUTION: Through running of a motor 18 with rake for a jack unit 6 housed in a jack house 2, a pinion 14 is spun in a direction of an arrow mark R through the medium of gears 17 and 16. A leg 3 gearing the pinion 14 through said function is guided by an upper and a lower guide, it projects downward, the forward end of the leg 3 seats the bottom of the sea, and it moves a marine working platform jack house 2 to a higher level. If the motor 8 with brake reverses, the marine working platform jack house 2 is lowered. Then, a load is transferred in a vertical direction by the aid of an upper spherical seat 11 and a lower spherical seat 10 formed on the upper part of the jack unit 6, and this permits the continuous measurement of the load applied to the upper part of the jact 6 through the working of a load gauge 12 and a buffer material 13 located on the under surface of the upper part of the jack house 2.