近年來，永續發展已成為全球趨勢，台灣亦規劃於 2026 年全面接軌 IFRS 永續揭露準則。隨著資本市場對永續報告書資訊之依賴程度日益提高，既有文獻多聚焦於企業是否揭露相關資訊，對於文本可讀性如何影響投資人決策與企業揭露策略之探討仍相對不足。基於此研究缺口，本研究依循信號理論與模糊假說，探討台灣上市櫃企業永續報告書之文本可讀性，是否能在報告發布期間為短期資本市場帶來顯著之累積異常報酬；同時進一步檢視企業營運績效，是否為影響報告書可讀性高低之關鍵因素。
考量台灣自 2022 年起對永續報告書實施新規範，本研究以 2022 至 2024 年間發布之永續報告書為樣本，共蒐集 2,371 筆有效觀察值。實證模型採用國立臺灣師範大學開發之文本可讀性測量工具擷取文本特徵；同時結合事件研究法進行量化分析，以檢驗報告發布期間之市場反應。
實證結果顯示，永續報告書之可讀性與發布期間之異常報酬呈顯著正相關，支持易讀文本能向資本市場傳遞正向訊號之觀點。其次，營運績效較差之企業，傾向發布可讀性較低且難詞比例較高之報告書，顯示管理階層可能透過提高文本複雜度進行印象管理。額外分析發現第三方永續評級對上述關係具有顯著負向調節效果，意即在評級壓力較高之情境下，績效良好企業提升報告可讀性之誘因反而受到抑制。
綜合上述發現，本研究建議主管機關未來修訂永續揭露規範時，除審查實質內容之完整性外，亦應將文字可讀性與資訊呈現品質納入監理考量。透過適度規範不具實質意涵之難詞使用，不僅有助於降低投資人之閱讀成本，亦能抑制企業利用晦澀語言進行印象管理或漂綠行為，進而提升永續揭露之整體資訊品質與市場信賴度。

The purpose of this study was to investigate the impact of the textual readability of sustainability reports on short-term cumulative abnormal returns among listed companies in Taiwan, based on signaling theory and the obfuscation hypothesis. Another aim was to examine whether operational performance determined the level of report readability. A quantitative research design was adopted. The study examined a sample of 2,371 sustainability reports published between 2022 and 2024. A textual readability measurement tool was applied to extract textual features, and the indices were reverse-transformed to represent higher readability. Furthermore, the event study methodology was conducted to analyze market reactions. The results revealed that the readability of sustainability reports was significantly and positively associated with abnormal returns. It was also discovered that firms with poorer operational performance tended to issue reports with lower readability and a higher proportion of complex words to engage in impression management. Furthermore, third-party sustainability ratings were found to exert a negative moderating effect, suppressing the incentive for well-performing firms to improve report readability due to regulatory pressures. The principal conclusion was that highly readable texts effectively conveyed positive signals to the capital market. Therefore, it is recommended that regulatory authorities incorporate textual readability into supervisory frameworks, regulating the use of meaningless, complex words to reduce investors' reading costs and deter corporate greenwashing.

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