Playing musical instrument has been suggested as one of the hobbies which can reduce risk of dementia. This study examined effects of three months training of playing the keyboard harmonica on older adults’ cognitive functions. Fifty elders who were 65 to 84 years old participated in this study. They were randomly assigned into either in control group or in experimental group. The experimental group had keyboard harmonica lessons for three months. Cognitive tests including a few tests of executive function, a language memory test, general cognitive function test, motor function tests, a questionnaire of emotional characteristics were measured before the lesson period, right after the lesson period, and three month from the end of the lessons. Nineteen participants in the experimental group and 18 participants in the control group were statistically compared. The results showed that playing and practicing the keyboard harmonica for three months with learning to read music scores helps to improve language memory of elders although it did not effect on their executive function nor emotional functions.