Abstract: A forming apparatus for forming a foamed body from a foamable plastic material under pressure control includes a pressure chamber, a mold unit, and a pressure-adjusting device. The mold unit is mounted in the pressure chamber, and includes an upper mold and a lower mold. When the upper and lower molds are interconnected, a mold cavity is defined therebetween. The plastic material is placed into the mold cavity so as to undergo cross-linking and foaming, thereby forming a blank. The blank generates a foaming pressure within the mold cavity. Subsequently, the pressure in the pressure chamber is adjusted to a forming pressure by the operation of the pressure-adjusting device so that the forming pressure is applied to the foamed blank so as to permit the foamed blank to expand, thereby forming the foamed body under the forming pressure.