The goal of this study was to assess the effect of a group exercise program on cognitive function of elderly people. Subjects were chosen to be elders with dementia having minor to moderate degrees of cognitive function. Study was started out by randomly dividing the 16 subjects into two groups, each with 8 people; the group exercise group and the control group. The group exercise group performed 8 weeks of group exercise program and general physiotherapy while the control group only performed general physiotherapy. Cognitive function was measured by Korean version mini-mental state examination. The study group's attention and calculation statistically significantly improved but the control group saw no statistically significant change. The group exercise program affected improvement in cognitive function of elderly people with dementia and in particular, was effective for enhancing their attention and calculation.