The objective of this study was to construct a speed feedback therapy system with a bicycle ergometer for elderly people with dementia and to assess its feasibility. There were 17 elderly people with dementia in the experimental group and 10 in the control group. In the experimental group, we used the system we devised in this study together with an ordinary ergometer. The Mini-Mental State Examination was performed before and after the interventions to evaluate their effects. No adverse effects occurred during use of the system. No changes in Mini-Mental State Examination scores were observed in the control group, but they increased significantly after the interventions in the experimental group. These results suggest that the speed feedback therapy system can be used as an intervention method to improve cognitive impairment in elderly people with dementia.