There are provided a support structures design device and method, a non-transitory computer readable recording medium storing a program, a structure forming apparatus, and a structure manufacturing method capable of appropriately adding the data of a support structures to the three-dimensional data of a luminal structure. The up-and-down direction of a luminal structure is determined, the core line of the luminal structure is extracted, a lowermost point of a cross section of the luminal structure by a plane perpendicular to a tangential direction at a point, which corresponds to each of a plurality of points on the core line, on a projected core line is extracted as a support point, and three-dimensional data is generated by adding the data of a support structures for supporting the support point to three-dimensional data.