A switching device for double nozzles of a 3D printer, which includes two transmission blocks, a rotary part and two spring parts. The two transmission blocks are in mirror image structures with each other and are respectively mounted on two nozzle devices; each transmission block is provided with a pressure supporting and transmiting portion, and the pressure supporting and transmiting portion includes a pressing-down stopping portion, a pressure transmiting portion, and a restoring stopping portion which are connected in sequence; the rotary part is connected to the case and is provided with two pressing parts; the two spring parts respectively sleeve the two nozzle devices, and the spring part supports the corresponding transmission block; the rotary part can rotate in a reciprocating manner, the rotary part drives the pressing parts to move on the two pressure supporting and transmiting portions.