In a trajectory determination device (40); a CAD data acquisition unit (41) acquires shape data representing the shape of a three-dimensional structure; a trajectory data generating unit (43) and layering conditions adjusting unit (44) generate, on the basis of the shape data acquired by the CAD data acquisition unit (41), control information which is information for controlling a layering device for layering molten metal for forming the structure and which indicates the trajectory for the layering device and/or layering conditions when the layering device layers molten metal such that the upper surface of one layer of a plurality of layers of molten metal layered is flat; and a control program output unit (45) outputs the control information generated by the trajectory data generating unit (43) and the layering conditions adjusting unit (44).

In a trajectory determination device (40); a CAD data acquisition unit (41) acquires shape data representing the shape of a three-dimensional structure; a trajectory data generating unit (43) and layering conditions adjusting unit (44) generate, on the basis of the shape data acquired by the CAD data acquisition unit (41), control information which is information for controlling a layering device for layering molten metal for forming the structure and which indicates the trajectory for the layering device and/or layering conditions when the layering device layers molten metal such that the upper surface of one layer of a plurality of layers of molten metal layered is flat; and a control program output unit (45) outputs the control information generated by the trajectory data generating unit (43) and the layering conditions adjusting unit (44).