The purpose of this study was to compare the levels of pre-service and in-service secondary science teachers' self efficacy beliefs relating to science teaching and to analyze the change of these beliefs according to their demographic characteristics such as gender, the graduate school type, teaching experience and major. The study was conducted with 50 pre-service secondary science teachers and 75 secondary science teachers. As the data collection instrument, the "science teaching efficacy belief scale" (STEBS) was used in this study. According to the research results, there was no significant difference between in-service and pre-service secondary science teachers' personal self efficacy beliefs and outcome expectations about science teaching at level alpha = 0.05. Moreover, these self efficacy beliefs and outcome expectations did not changed relating to their gender, teaching experience, but they changed relating to their graduate school type and major. (Contains 10 tables.)