To tilt a jack-up cylinder by a simple configuration without giving a burden to a worker.

In a jack-up device which has a jack-up cylinder 5 supported centered on a predetermined rotary shaft so as to turn an holds the jack-up cylinder 5 in a condition in which it is substantially vertical for the ground surface when it is used and in a storage condition in which the cylinder 5 is tilted when it is not used, a rope 14 of which both ends can be connected with a tube 5a and a rod 5b of the cylinder 5, respectively, and a rope hooking member 15 by which the rope 14 is stretched around between the tube 5a and the rod 5b are provided. By tilting the cylinder 5 in which the rope 14 pulled due to the expansion of the rod 5b is in a substantially vertical condition toward a storage condition and loosening the rope 14 due to the shrinkage of the rod 5b, the cylinder 5 in the storage condition turns toward the vertical condition due to its empty weight.