The invention discloses a 3D printing device and a 3D printing method by utilizing supercritical carbon dioxide as a solvent. The device mainly comprises a stock unit, an ejection unit, a three-dimensional molding platform unit and a raw material recycling unit, wherein the ejection unit comprises a gas pump, a needle valve, a cooling fan and a resistive heater; the stock unit comprises high polymer material powder, a powder pump, a carbon dioxide gas cylinder, a mixing tank, a liquefied booster pump, a heater, a liquid pump and a gas pump; the three-dimensional molding platform unit comprises an aluminum alloy molding platform and a three-dimensional ball screw sliding table module; and the raw material recycling unit comprises a closed box and a recovered gas pump. According to the method disclosed by the invention, the carbon dioxide gas is turned to be in a supercritical carbon dioxide state, and after the carbon dioxide gas is completely dissolved to produce supercritical carbon dioxide solution containing a high polymer material, the solution is conveyed into the ejection unit by virtue of the liquid pump. The supercritical carbon dioxide serves as a consumable carrier, so that more kinds of high polymer materials are applied to the field of 3D printing, and the overall performances of 3D printing supplies are improved.