The major purpose of this study was to develop a survey to measure elementary school teachers' self-efficacy for web-based professional development. Based on interviews with eight elementary school teachers, three scales of web-based professional development self-efficacy (WPDSE) were formed, namely, general self-efficacy (measuring teachers' general capabilities of using Internet tools or completing basic web-based tasks), interaction self-efficacy (assessing teachers' perceived abilities of engaging in interactions in online professional development activities), and applying self-efficacy (evaluating teachers' confidence level of applying what they have learned in web-based professional development to their future teaching). The results of Exploratory Factor Analysis (EFA) indicated that the three scales of WPDSE arising from the interviews and the Cronbach alpha values, ranging from 0.92 to 0.85, were acceptable. Subsequently, a large-scale survey was conducted to examine the relationships between teachers' self-efficacy and attitudes toward web-based professional development with a sample of 214 elementary school teachers in Taiwan using a questionnaire that included WPDSE and an established scale for measuring attitudes toward web-based professional development (AWPD). The results indicated that teachers' self-efficacy played a positive role in their attitudes towards web-based professional development. The results also indicated that teachers' confidence in their interaction self-efficacy and in their applying self-efficacy was more important than their confidence in their general self-efficacy in predicting their attitudes toward web-based professional development. Implications of the study findings were also discussed.