The purpose of this study was to investigate the relationship between personality and characteristics in rhythm-improvisation of music. Sixty-eight undergraduates were asked to fill out a Five-Factor Personality Questionnaire (FFPQ) and to improvise musical rhythms on 6 types of percussion instruments. As a result, it was suggested that some personality traits were reflected in specific characteristics of expression in rhythm-improvisation of the music. In addition, these results suggest that some affects were influenced by specific characteristics of expression in musical rhythm improvisation. These findings suggest that some personality traits can be characterized by the types of rhythm-improvisation and the affects of improvisation has more influence on it. These results may be used as one of the initial objective indicators for music therapy.