A press forming device for performing a first step of bend-forming a base sheet or a material to be processed obtained by applying bending or drawing to a base sheet beforehand into a hat cross-sectional shape having a top sheet portion and right and left vertical wall portions (1Ba, 1Bb) continuous to both sides in a width direction of the top sheet portion and not having a flange portion and a second step of applying compression by a preset compression amount in a direction along a press direction to the vertical wall portions in a formed state by the first step, the press forming device comprising: a punch and a pad sandwiching the top sheet portion between the punch and the pad in a sheet thickness direction; bending blades disposed on sides of the punch and the pad and bend-forming the vertical wall portions; and stoppers facing the bending blades in the press direction and constraining end portions of the material to be processed, wherein the pad and the bending blades configure an upper die, the punch is supported by a first cushion component elastically expandable and contractible in the press direction, characterized in that the bending blades each have an upper die component and a lower die component vertically divided in an arbitrary location capable of facing the vertical portion of the vertical wall portion having the hat cross-sectional shape and by a plane crossing with the press direction in the middle of the press direction and disposed facing each other in the press direction with an interval equal to or larger than the compression amount to be applied and a second cushion component interposed between the upper die component and the lower die component, maintaining the interval, and contractible in the press direction at a predetermined pressure or more, and cushion pressure of the second cushion component is lower than cushion pressure of the first cushion component and has such cushion pressure that the second cushion component does not contract during the bend-forming of the vertical wall portions in the first step. a punch and a pad sandwiching the top sheet portion between the punch and the pad in a sheet thickness direction; bending blades disposed on sides of the punch and the pad and bend-forming the vertical wall portions; and stoppers facing the bending blades in the press direction and constraining end portions of the material to be processed, wherein the pad and the bending blades configure an upper die, the punch is supported by a first cushion component elastically expandable and contractible in the press direction, characterized in that the bending blades each have an upper die component and a lower die component vertically divided in an arbitrary location capable of facing the vertical portion of the vertical wall portion having the hat cross-sectional shape and by a plane crossing with the press direction in the middle of the press direction and disposed facing each other in the press direction with an interval equal to or larger than the compression amount to be applied and a second cushion component interposed between the upper die component and the lower die component, maintaining the interval, and contractible in the press direction at a predetermined pressure or more, and cushion pressure of the second cushion component is lower than cushion pressure of the first cushion component and has such cushion pressure that the second cushion component does not contract during the bend-forming of the vertical wall portions in the first step.