This study aims to develop and evaluate competency-based web learning material (CBWLM) for the college practicum Microprocessor Laboratory. After using the CBWLM for 8 weeks, this study investigates CBWL's learning effects and self-directed learning aptitudes (SDLAs) as well as exploring the influence of SDLA on learning effects based on the sample of 38 students. The results of this study indicate that over half of the students achieve the mastery level after using CBWLM. SDLAs of the mid-CBWL and post-CBWL do not influence learning effects. (Contains 11 tables and 3 figures.)