The purpose of this study is to investigate dynamic characteristics of retractable spatial structures. To this end, Kometsu dome located in Japan was selected as an example structure. Structural properties and dynamic characteristics of Kometsu dome was evaluated in this paper. Natural periods of the Kometsu dome with closed roof system was compared those with opened roof system. Generally, snow loads are main concerns in structural design of spatial structures. Roof snow loads can be substantial and they can put a real strain on a spatial structure. Especially, roof snow loads can change dynamic characteristics of the spatial structures. If the dynamic characteristics of the spatial structures is changed, control performance of tuned mass dampers installed on the roof structure will be deteriorated. Therefore, variation of the dynamic characteristics of the retractable spatial structure was investigated in this paper.