Purpose : This study was to evaluate the effects of cognitive rehabilitation training on the cognitive decline of dementia patients. Therefore the purpose of this study was to examine the influence of brain activation according to bio-feedback training in dementia. Methods : Ten dementia patients were recruited this study. Experiment was performed for 30min per session, five times a week through 4 week and two measurements before and after bio-feedback training. Brain activity was measured by Korea Electroencephalogram(EEG) system. Statistical analysis was used Wilcoxon signed rank test to know difference of EEG between pre and post-test in each group and Mann-Whitney U test was to know difference between experimental and control group. Results : Significant improvement of slow-alpha wave was observed following bio-feedback in experiment group. There was no significant change in experiment and control group. Conclusion : In this study, the bio-feedback training was effective in improving slow-alpha wave in dementia patients. It is suggested that bio-feedback training with dementia patients can be useful to ameliorate the cognitive decline. And it will be effective for prevention of cognitive function decline.