In this study, the author investigated the relationship between the layout of objects placed on a table and tidying up. The author developed a system that can tidy up through cooperation between a robot and human. For realizing this system, it was necessary to investigate the types of instances in which people think a table top is disorderly. The author conducted an experiment in which participants were asked to evaluate the disorder condition of presented table images. The participants were also asked to answer how many objects on a table would be collected into groups. The results indicated that objects organized into more groups were rated as untidier than objects organized into fewer groups.