The lexical literacy environment refers to the ‘language literacy environment that affects the development of lexical competence’. This study causally revealed the relationship between learners’ lexical competence and lexical literacy environment through SEM analysis. About 2,000 learners(third year) from 24 middle schools across the country were analyzed as a sample. As a result, it was found that ‘vocabulary learning activeness, parents’ academic background, enjoyment of reading, attitude toward lexical competence’ had a positive effect on learners’ vocabulary scores, and the more negative the learners perceived the ‘vocabulary teaching and learning situation at school’, the higher the vocabulary score. As a result of the analysis between the male and female groups, the difference between the structural equation path coefficients was mostly not statistically significant, but the ‘attitude toward lexical competence’ had a much greater effect in the female group.