This research aims to gather a basic data to study the clinical use of art materials based on collected clinical empirical data from art therapists who have experience using group art therapy within a mental health care ward. The study conducted focus group interviews with 12 art therapists, divided into two different groups based on their clinical experience. Findings of this study show; First, art materials were selected by art therapists with thorough consideration based on clinical setting, severity of patients’ symptoms, use of art materials, art therapist s style, and purpose of art therapy. Second, art materials were used most effectively when art therapists provided indirect social experience or encouraged participation from their patients. Third, the art therapists experienced that art materials created positive changes in patients via amplified self-expression. Fourth, the use of art materials in group art therapy had difficulties due to different clinical settings as well as various patients symptoms. However, proper handling by art therapists was observed during the preparation and program activities. This study indicates how art materials apply to clinical practice in a mental health care ward, and this may be useful as basic data on clinical use of art materials and for future research.