With the expansion of ESG management, the importance of sustainability reports has been continuously emphasized, and the number of companies disclosing sustainability or ESG reports has increased. However, in-depth research on the quality of these reports and methodological analyses of their evaluation remain limited. Therefore, this study applied an integrated evaluation framework that combines the SRQ(sustainability reporting quality) model proposed by Permatasari et al.(2020) and the GRI(global reporting initiative) Standards to explore the quality of sustainability reports of a leading Korean refining company. Specifically, a framework consisting of six core domains and twenty sub-criteria, aligned with international standards, was constructed and applied to the most recent three sustainability reports(2022~2024) published by SK Innovation. The analysis provided quantitative assessments of the quality level and signals of change across the years. Two rounds of evaluation(initial and re-evaluation) were conducted using the same codebook, and both reliability(ICC, paired t-test, effect size) and validity(responsiveness SRM, rank concordance Kendall’s W) were examined. The results demonstrated that the reliability was good to excellent with no evidence of systematic bias. In terms of validity, significant responsiveness and moderate consistency in domain rankings were observed, suggesting that the proposed framework can effectively capture actual changes in the quality of sustainability reports in the refining industry. Moreover, this study contributes by presenting a codebook tailored to the refining sector, thereby highlighting its practical applicability. Nevertheless, the study has limitations in that the evaluation was conducted by a single assessor on the sustainability reports of a single company. Future research should expand both evaluators and research targets to enhance the generalizability of the findings.