The problem to be solved is, when printing a 3D object by using a 3D printer of fused-deposition-modeling type or another type, to enable printing it even when the filament is not supported from underneath by avoiding filament drop by generating force to push the extruded filament to the neighbor filament, and to enable arraying the filaments to a horizontal direction.To avoid filament drop, force that pushes the newly extruded filament to the neighboring filament is generated, and filament drop is avoided. To do so, compression or extension power is generated by controlling the filament cross section by controlling the filament cross-section (i.e., the extrusion amount) and stiffness of the filament is controlled by controlling the temperature or light.