Abstract. [Purpose] In this study, we investigated the effect of exercise using a horse-riding simulator on the physical ability of frail seniors.[Subjects] The subjects consisted of 21 frail seniors living in the vicinity of a day care facility, which they used more than twice each week.[Methods] The subjects were randomly divided into two groups, an exercise group and a control group. The exercise group, in addition to their normal exercise routine at the day care facility, participated in exercise using a horse-riding simulator. The control group continued their normal exercise regime at the facility with no additional exercise. The duration of our research was 12 weeks.[Results] The levels of physical ability of the exercise group were significantly increased after the implementation period relative to the pre-study levels. On the other hand, there was no significant difference in the pre-and post-study levels of the physical ability of the control group. In addition, even in the exercise group, no significant difference in the levels of more complicated movement abilities relative to those of pre-study abilities was observed. [Conclusion] Although the level of physical ability of some frail seniors was increased by exercise using the horse-riding simulator, the exercise did not realize a sufficient increase in the levels of all movement abilities.