PURPOSE: To provide a system for assembling a three-dimensional object by which it is possible to easily perform the assembling work under computer control. CONSTITUTION: A closed loop extrusion system 10 comprises a nozzle 12 for extruding a material such as a hot melt adhesive, devices 14, 18, 46 for positioning the nozzle 12 in a freely controllable manner according to specifications and a sensor 60 which generates a feedback signal showing at least one of the characteristics of parts extruded anew using the material. A nozzle positioning device includes a support stage, for an object, which reacts to a nozzle activation list stored in a controller 46 for moving the nozzle 12 horizontally within an x-y plane and further moves the nozzle 2 perpendicularly along the x axis. In addition, the nozzle positioning device is activated to move the nozzle 12 on the z axis.