To provide a hydraulic forming method capable of feeding a plate to a hydraulic pressure chamber without buckling the plate even when the metal plate to be formed is thin when performing the hydraulic forming of the plate, and a hydraulic forming die having a plate feeding device capable of feeding the plate to the hydraulic pressure chamber without buckling the plate.

In the hydraulic forming for obtaining a formed product copied to a forming shape of an inner periphery of a forming chamber 14 by pressure-filling a liquid into the forming chamber 14 formed in a forming die 10 composed of an upper die 11 and a lower die 12, and swelling a plate 13 to be formed held between the upper die 11 and the lower die 12 in the forming chamber 14, a peripheral edge of the plate 13 is held by a blank holder 35 while being pressurized in the thickness direction, and the plate 13 is fed to the forming chamber 14 by moving the blank holder 35 in an advancing/retracting manner to/from the forming chamber 14.