To provide a structure automatically connected in objective three- dimensional shape without any external assistance using a self-traveling unit for forming optional three-dimensional shape.

An automatic assembly of a three-dimensional structure is composed of a plurality of assembly units 1 each of which is provided with a unit body 10 positioned at the center, rotating arms 11 extended in the respective directions of three-orthogonal axes from the unit body 10 and rotatory- driven in relation to the unit body, and connecting mechanism 12 provided at the tip of each rotating arm 11. The unit body 10 is provided inside with a single motor for rotatory-driving each rotating arm 11 and putting the connecting mechanism 12 in engaging/disengaging action, and an information processor for controlling the action of the assembly unit 1. The connecting mechanism 12 is mechanically connectble to each connecting mechanism in the other assembly unit 1, and information can be exchanged between the information processors.