The present invention provides a hydroforming method able to increase the expansion ratio to obtain a complicated shape hydroformed product and able to reduce the number of steps of work, that is, a hydroforming method loading a metal pipe into a divided mold, clamping the mold, then applying an internal pressure and pushing force in the pipe axial direction to said metal pipe, comprising, in a first hydroforming step, expanding said metal pipe in one direction of said metal pipe cross-section to obtain an intermediate product having a circumferential length of 90% to 100% of the circumferential length of the product shape in all of the expanded part in the pipe axial direction and having a height greater than the height of the product in said one direction and at least part of the pipe axial direction, then, in a second hydroforming step, reducing the height in the one direction of said intermediate product in all or part of the pipe axial direction while shaping the product to the final product shape. Further, in the case of a shape including bending, a bending step is performed between the above first hydroforming step and second hydroforming step.