我國所得稅法自民國八十七年一月一日開始實施兩稅合一制度。這原本是政府一項消除重複課稅的美意，但是仍受到多方批評。其爭議點就在於「未分配盈餘加徵百分之十營利事業所得稅」這項配套措施的實施。許多專家學者認為，對企業的未分配盈餘課稅，不利於企業內部資金的累積，進而影響其創新活動的投入與產出。而財政部卻持有不同的看法。 基於上述爭議，本研究以迴歸模式探討「未分盈餘加徵百分之十營利事業所得稅」制度的實施，對企業創新活動的影響。經實證結果發現： 1.對企業未分配盈餘加徵10%營利事業所得稅，確實會影響企業資本形成，降低其創新活動。因此，為求稅制良善，促進國家經濟發展，政府對於稅制之設計應謹慎為之。 2.以高科技產業和傳統產業比較，高科技產業由於兩稅合一未分配盈餘加徵10%營利事業所得稅制度的實施，其創新活動較制度實施前縮減，且縮減程度明顯大於傳統產業。此結果顯示，高科技產業顯然可謂新稅制下的最大受害者。因此，對高科技產業之未分配盈餘加以課稅，無疑是形成其創新活動的絆腳石、增加其營運上的風險。政府對此情況，應予正視。 3.以融資受限公司和融資未受限公司比較，兩稅合一之未分配盈餘加徵10%營利事業所得稅制度對融資受限公司之影響不大。經分析樣本特性，發現融資受限公司的獲利能力較差，因此租稅課徵對於其所造成的影響較低。因此可推論，獲利能力差之融資受限公司的創新活動受到非租稅因素的影響比租稅因素來得大。 關鍵字：未分配盈餘加徵百分之十營利事業所得稅，兩稅合一，創新活動 / In response to the public concern, Taiwan has adopted the imputation tax credit system since January 1st, 1998. Although the new tax reform can eliminate double taxation, the implementation of additional 10% surtax on undistributed surplus earnings has engendered lots of comments. Based on the disputations resulted from the new tax system, we conduct an empirical research analyzing the impacts of the implementation of additional 10% surtax on undistributed surplus earnings on the enterprises’ innovation. The empirical results in this research can be summarized as follows: 1. Imposing 10% surtax on corporate undistributed surplus earnings has adverse effect on capital accumulation, in turn leading to reduction in incentive of enterprises to conduct innovative activities. 2. Compared to the traditional industry, adverse effect of this new system is more profound for firms in the high-tech industry. The results indicate that high-tech industry is the major victim under the new tax reform. Therefore, imposing additional 10% surtax on high-tech industry will be an obstacle to enterprises’ growth and increase its operating risks. 3. Compared to unconstrained firms, we find out that the new tax system have less effects on constrained firms. Owing to considering the poor profitability, we can infer that non-tax factors have greater influence on the innovation of constrained firms relative to tax factors. Key words: additional 10% surtax on undistributed surplus earnings, the imputation tax credit system, innovation