A fused deposition modeling (FDM) is widely used as a 3D printing method of plastics (polymeric materials). However, modeling of soft materials is conventionally quite difficult using such method although 3D printing of plastics and/or elastomers is required for medical application such as manufacturing of prosthetic arms and legs. In this study, we investigated the optimum 3D printing conditions for modeling of spherical objects made with FABRIALTM-R and -H (JSR corp.). First, we 3D printed spherical objects with various nozzle speeds. Then, we observed the surfaces of 3D printed objects using a stereoscopic microscope. In addition, the hardness of the objects was measured by using a durometer (type E, Japanese Industrial Standards). The results suggest that optimum nozzle speed is 2.0 mm/s or less. Furthermore, the hardness of FABRIALTM-R object was dependent on nozzle speed while that of FABRIALTM-H was constant. These findings are expected to be applied to modeling of parts of prosthetic arms and soft-matter robots.