According to literature review, student teachers often encounter problems regarding teaching-related practices, anxiety on practicum, and interpersonal relationships with school personnel. Social media can provide information and support. The purpose of this study is to investigate what social media can benefit student teachers in. A Facebook Group for Taiwanese interns was built. A quasi-experimental pre- and post-test control group design was employed among student teachers. The analysis of the validated questionnaires consisted of 105 in E-Group and 40 in C-Group. This study concludes that social media use benefited student teachers in decrease of teacher anxiety on practicum; however, the use cannot promote their pedagogical content knowledge, neither strengthen their interpersonal interaction with school personal.