We evaluated our previously proposed technique of protecting the copyrights of digital data for 3-D printing. This technique embeds copyright information into not only digital data but also fabricated objects and enables the information to be read to reveal possible copyright violations. The insides of fabricated objects are constructed with fine cavities to embed information into them. In this study, the readability of embedded information relating to the structure parameters of the fine cavities inside fabricated objects was examined to clarify the conditions in which this technique can be applied. The top-view sizes of the cavities, the top-view spaces between cavities, the depths of the cavities themselves, and the depths of the cavities from the surfaces of the objects were changed as experimental parameters. Experimental results clarified the conditions for forming cavities inside the fabricated objects and showed that a sufficient amount of information for copyright (i. e., hundreds of bits) could be embedded if a fabricated object was several centimeters in size.