A hydroforming apparatus and working method able to simply find a load path are proposed, which system and method use a mold in which contact sensors able to judge contact with a metal tube inside the mold are mounted at least at two different positions in the tube axial direction, perform a first step of axially pushing tube ends in a state with the internal pressure held at a constant value and stopping the progress of the axial pushing action when judging that among the contact sensors not yet in contact mounted at positions closest to the tube ends detect contact with the metal tube, next perform a second step of raising only the internal pressure while leaving the positions of the tube ends fixed and stopping the increase in the internal pressure when the contact sensor not yet in contact judges contact, next perform a third step of lowering the internal pressure to the value before raising it while leaving the positions of the tube ends fixed, and repeat said first step to third step until all of said contact sensors judge contact so as to obtain a hydroformed part.