A hot isostatic pressing device for performing hot isostatic pressing processing to a workpiece, the hot isostatic pressing device comprising: a gas-impermeable casing that has gas impermeability and is arranged so as to surround a workpiece, the casing including a casing body having a lower-side opening, and a casing base that closes the lower-side opening of the casing body; a heating unit that is provided inside the casing so as to form a hot zone around the workpiece, thereby making it possible to perform hot isostatic pressing processing to the workpiece by using a pressure-medium gas in the hot zone; a high-pressure container that surrounds a space where the heating unit and the casing are housed and that includes a base that closes the space from below; and a cooling unit that cools the hot zone by guiding, into the hot zone, the pressure-medium gas having been cooled while flowing from above to below outside the casing, wherein the cooling unit includes: a gas introduction unit that guides the pressure-medium gas cooled outside the casing, from a lower part of the high-pressure container to an upper part of the hot zone, in such a manner that the pressure-medium gas does not meet the pressure-medium gas inside the hot zone, and introduces the pressure-medium gas guided to the upper part of the hot zone into the hot zone; and a cooling promotion unit (37; 40) that cools the pressure-medium gas having been cooled outside the casing by allowing the pressure-medium gas to exchange heat with the base, characterized in that a gas storage unit that stores the pressure-medium gas to be introduced to the gas introduction unit is provided between the base and the casing base, in a state of being separated from the space outside the casing, and the cooling promotion unit (37; 40) sends the pressure-medium gas having exchanged heat with the base to the gas storage unit. a gas-impermeable casing that has gas impermeability and is arranged so as to surround a workpiece, the casing including a casing body having a lower-side opening, and a casing base that closes the lower-side opening of the casing body; a heating unit that is provided inside the casing so as to form a hot zone around the workpiece, thereby making it possible to perform hot isostatic pressing processing to the workpiece by using a pressure-medium gas in the hot zone; a high-pressure container that surrounds a space where the heating unit and the casing are housed and that includes a base that closes the space from below; and a cooling unit that cools the hot zone by guiding, into the hot zone, the pressure-medium gas having been cooled while flowing from above to below outside the casing, wherein the cooling unit includes: a gas introduction unit that guides the pressure-medium gas cooled outside the casing, from a lower part of the high-pressure container to an upper part of the hot zone, in such a manner that the pressure-medium gas does not meet the pressure-medium gas inside the hot zone, and introduces the pressure-medium gas guided to the upper part of the hot zone into the hot zone; and a cooling promotion unit (37; 40) that cools the pressure-medium gas having been cooled outside the casing by allowing the pressure-medium gas to exchange heat with the base, a gas introduction unit that guides the pressure-medium gas cooled outside the casing, from a lower part of the high-pressure container to an upper part of the hot zone, in such a manner that the pressure-medium gas does not meet the pressure-medium gas inside the hot zone, and introduces the pressure-medium gas guided to the upper part of the hot zone into the hot zone; and a cooling promotion unit (37; 40) that cools the pressure-medium gas having been cooled outside the casing by allowing the pressure-medium gas to exchange heat with the base, characterized in that a gas storage unit that stores the pressure-medium gas to be introduced to the gas introduction unit is provided between the base and the casing base, in a state of being separated from the space outside the casing, and the cooling promotion unit (37; 40) sends the pressure-medium gas having exchanged heat with the base to the gas storage unit.