A 3D printer has a dual stage structure and includes: a frame; an extrusion unit having a nozzle configured to extrude a raw material; a stacking base unit positioned under the extrusion unit and configured to receive the raw material on a surface thereof so that an object is formed in a layer-by-layer manner on the surface; and a cutting unit positioned between the stacking base unit and the extrusion unit and configured to grind or cut the object formed on the surface of the stacking base unit, wherein the frame is configured to be connected to outer sides of the stacking base unit, the extrusion unit, and the cutting unit, the stacking base unit and the cutting unit are configured to be vertically movable along the frame, and the nozzle is configured to be movable on a plane.