Based on the knowledge gap hypothesis as a theoretical framework, the present study examines (a) whether there is an education-based gap in misinformation acceptance, (b) whether the education-based gap could be explained by differences in issue knowledge, information processing, and media dependency, and (c) whether the education-based gap in misinformation acceptance widens as the level of exposure to misinformation increases. We conducted a survey of 821 Korean adults regarding their acceptance of misinformation related to COVID-19 vaccination. First, we found that there was an education-based gap in misinformation acceptance such that those with lower education were more likely to accept misinformation. Second, we found that the effect was mediated by low issue knowledge, less systematic processing, and dependency on social media. Third, the education-based gap in misinformation acceptance widened when misinformation exposure increased. These results are consistent with the knowledge gap hypothesis and the theoretical and practical implications are further discussed.