Physics subjects or topics as a part of science education enable students to explore nature and natural events by using physics laws and scientific methods. In the lower-secondary school, physics is a subfield within the science curriculum developed holistically with the broad field curriculum design unlike the subject-centred curriculum in the upper-secondary education. As an important factor that directs the achievement, self-efficacy is one of the predecessors of these cognitive and affective skills. Accordingly, most of the scales which evaluate the students' cognitive or affective skills in the lower-secondary school are related to science course in a general context. This research aimed to develop a valid and reliable scale measuring the students' self-efficacy beliefs toward physics subjects for lower-secondary schools. The sample consists of 2737 students. The draft scale consisted of 52 items and was applied to 1882 students in the first stage. To construct validity of the scale, exploratory factor analysis was performed. The results showed that the scale consisted of single- factor with 28 items. To confirm its factor structure, the scale was applied to 785 students. The research findings indicate that the scale is a valid and reliable instrument to measure the self-efficacy beliefs towards physics subjects.