To synchronize the ascending/descending movement of first and second hydraulic cylinder devices by a simple structure, and also improve the distributivity of pipings between both these hydraulic cylinder devices.

In this synchronous hydraulic cylinder device 30, a first hydraulic cylinder device 30A having a cylinder 31 and an outer cylinder 32 and a second hydraulic cylinder device 30B having a cylinder 36 are used, the oil chamber cross sectional area A1 of the rod side oil chamber 34A of the first hydraulic cylinder device 30A and the rod cross sectional area A2 of the piston rod 37 of the second hydraulic cylinder device 30B are made the same, and the second port 35B of the first hydraulic cylinder device 30A and the oil chambers 38A, 38B of the second hydraulic cylinder device 30B are communicated with each other by a hydraulic conduit 39.