Few studies have developed questionnaires that attempt to assess approaches to learning in the context of Internet-based learning. To obtain a better understanding of undergraduates' approaches to Internet-based learning, this study aimed to develop and validate the Approaches to Internet-based Learning (AIL) instrument which was created by referring to the qualitative results of Ellis' (2011) research and the structure of Lee et al.'s (2008) Approaches to Learning Science questionnaire. The AIL consists of the six factors of "deep motive," "criticism and evaluation", "reflection and integration," "surface motive," "collecting and summarizing," and "replicating information." In addition, the former three factors could be categorized as "Deep approaches to Internet-based learning" while the latter three could be grouped into "Surface approaches to Internet-based learning." To establish the reliability and validity of the AIL and to confirm its second-order structure as hypothesized in this study, exploratory factor analysis and second-order confirmatory factor analysis were conducted. A total of 598 undergraduates from seven Taiwanese universities participated in this study. The results support our hypothesized second-order structure of the AIL and indicate that the instrument items have good reliability and validity. We also found that the Taiwanese undergraduates tended to adopt deep approaches to Internet-based learning. The newly developed AIL could provide educators with a valid instrument to examine students' approaches to Internet-based learning.