We introduce Swarm Fabrication, a novel concept of creating on- demand, scalable, and reconfigurable fabrication machines made of swarm robots. We present ways to construct an element of fabrica- tion machines, such as motors, elevator, table, feeder, and extruder, by leveraging toio robots and 3D printed attachments. By combin- ing these elements, we demonstrate constructing a X-Y-Z plotter with multiple toio robots, which can be used for drawing plotters and 3D printers. We also show the possibility to extend our idea to more general-purpose fabrication machines, which include 3D printers, CNC machining, foam cutters, line drawing devices, pick and place machines, 3D scanning, etc. Through this, we draw a future vision, where the swarm robots can construct a scalable and reconfigurable fabrication machines on-demand, which can be deployed anywhere the user wishes. We believe this fabrication technique will become a means of interactive and highly flexible fabrication in the future.