The main aim of the study is to evaluate the impact of the competency-based web learning material (CBWLM) on the self-directed learning aptitude (SDLA) of college students. Specifically, it seeks to investigate, statistically, the changes in SDLAs at different stages of competency-based web learning (CBWL) over an eight-week period. The sample of this study consists of 38 students from the practicum "Microprocessor Laboratory", a sophomore course at a college. The result of the study reveals that no significant changes in SDLA test scores (before, during and after working in the CBWLM) are found. Specifically, it implies the CBWLM does not have significant influence on the students' overall SDLA, but slightly enhances their "Fondness for Learning" factor in SDLA. Recommendations proposed by the study are to develop more superior CBWL materials and extending the duration of CBWL.