To hold a horizontal of an upper surface of a lifter table even when an unbalanced load is applied.

A plurality of lifter arms 11 assembling in crossed shape a first/second arm 7, 9 connecting between a base stand 3 and a lifter table 5 are provided in parallel, a first/second hydraulic cylinder 31, 39 is provided respectively between the first/second arms 7, 9. Rod side areas of the first/ second hydraulic cylinders 31, 39 are formed in an equal area, by connecting rod sides of the first/second hydraulic cylinders 31, 39 to provide a series circuit, the lifter table 5 can hold a horizontal even by applying an unbalanced load. The series circuit can be switched to a parallel circuit at lowering down time, so as to always supplement oil, a stroke of both the hydraulic cylinders 31, 39 is also uniformly maintained.