To provide a hydraulic spring system of characteristics variable type capable of freely adjusting the characteristic values as a spring.

The hydraulic spring system is equipped with a moving member 10 to reciprocate in compliance with the load, an oscillating piston and cylinder mechanism 11 with one end connected rotatably with the moving member 10 and the other end connected rotatably with a stationary system and arranged with a certain angle with respect to the moving direction of the moving member 10, and an oscillation side oil pressure supplying means 12 to supply a constant oil pressure into the piston and cylinder mechanism 11, and is structured so as to push back the moving member 10 by the piston and cylinder mechanism 11 with a spring constant complying with the fed constant oil pressure when the moving member 10 makes movement, wherein the oscillation side oil pressure supplying means 12 has an oscillation side oil pressure ratio changing mechanism 23 to change the spring constant by regulating the size of the constant oil pressure supplied into the mechanism 11.

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