The invention discloses a 3D printing device and method. The device comprises a printing chamber, a feeding device, a moving support, a printing spray head, a heating body, a pneumatic controller, a printing platform, a mechanical arm and a repairing tool bit. 3D printing is conducted in a melt extrusion condensing mode, the temperature difference of a material sprayed by the printing spray head and a workpiece is strictly controlled, the consistence and quality of the printed and condensed material are guaranteed, the requirement for the material is low, and most of the material can achieve 3D printing. In addition, the printing chamber is provided with the mechanical arm and the repairing tool bit which are used for printing and repairing on the workpiece at the same time, and the 3D printing technology is finally achieved. The 3D printing device and method have the advantages that precision is high, and the range of materials which can be machined is large.