Abstract: A creep preventing safety device for hydraulic jacks, especially of the type employed for partially or one-side raising road vehicles, but not limited thereto, and comprising a bearing frame having journalled thereto the lifting arm of a force applying cup and its related parallel translation linkage, between opposite side plates of the frame there being accommodated the power applying hydraulic unit proper, along with the primary actuating lever and the foot lever for controlling the force applying cup, which hydraulic unit has its piston and piston rod operatively connected to said lifting arm; the creep preventing device being provided with a ratchet mechanism intervening between said power applying hydraulic unit and the lifting arm and including means for controllably releasing said ratchet mechanism.