The purpose of this study was to test the effects of music therapy on cognitive function and depression in demented old adults. This study was made with one-group in a pre- and post-test design. The subjects were seven demented old adults over, sixty-five years and with mild to moderate cognitive impairment, residing at a nursing home. Music therapy was given by one researcher and one research assistant for thirty to forty minutes twice a week for 4 months. Music therapy was conducted with the subjects both listening and singing with a cassette player and a double-handed drum. In order to evaluate the effects of music, we measured the level of cognitive function and depression at the beginning and at the end of the music therapy session by means of an MMSE-K developed by Kwon and Park and the Depression Inventory developed by Chon. The Data were analyzed using descriptive statistics and a paired t-test analysis using a SPSS PC package. The results are as follows: 1) The subjects of the music therapy showed improvement in cognitive function. The MMSE-K score was significantly increased after music therapy. Especially, memory recall was very significantly. 2) The subjects of the music therapy showed a slight decrease in depression. However, there was no significant difference in the degree of depression between mean scores measured before and after music therapy. The results suggest that music therapy is effective in improving and maintaining cognitive function in demented old adults. And we suggest that long-term music therapy will be required to improve depression in demented old adults. These findings are encouraging the idea that music therapy may improve cognitive impairment.