This study conducted a survey to examine the knowledge formation and utilization of computer among beginning teachers of secondary school mathematics. We found that beginning teachers who had more experiences of taking computer utilization classes at teacher education institutes showed more interest in computer and saw the necessity and effectiveness of computer usage for teaching students. Teachers chose GSP the most among computer utilization knowledge learned in pre-service teachers program, and GSP is used the most in mathematics classes. However, they answered that computer is not so much available in class due to lack of hours and the relevant resources. Lastly, beginning teachers answered that the computer knowledge learned in in-service teacher program was more useful than that in pre-service. Thus, the professional development in utilizing computer should be improved through diversifying teacher training contents for beginning teachers as well as for pre-service teachers in teacher education institutes.