A unit for constructing a robot with units, wherein a joint unit comprises joint means and is organized in a joint casing having a surface profile of a dice-like cube, or a uniaxial cylindrical body, or an orthogonal dual-axis cylinder-like cubic with a uniform joint means separation distance. The joint means comprises N positioning projections disposed about the center axis thereof at equal intervals and equal angles and N connecting screw holes respectively disposed at positions rotated from these projections by 360°/2N about the center axis thereof. Also, a zero-degree joint power transmission unit converts and transmits the rotations of the joint unit rotated, by itself, relative to an input joint fixed shaft fixed to the joint casing, to the rotations of an output rotating shaft disposed a joint unit separation distance away therefrom.