A crimping apparatus comprising a press module connected with a pressing mold, a translation module, and a pressure control module is disclosed. The press module generates an action force on the pressing mold through a fluid. The translation module is coupled to the press module for driving the press module to move toward a flexible printed circuit having two isolated circuit layers such that one circuit layer is pressed to crimp to the other circuit layer, wherein the pressure control module adjusts the pressure within the press module to maintain a constant force on the pressing mold whereby the pressing mold can generate a constant stress acting on the flexible printed circuit during the crimping process. In addition, the crimping apparatus can be adapted in a roll-to-roll process for crimping two isolated circuit layers of each flexible printed circuit unit arranged on the roll.