傳統探討利潤移轉效果的租稅競爭文獻中，忽略廠商租稅規避效果對公共財的影響。然而，在貿易自由化與國際化興盛的時代下，廠商對於國與國之間的租稅安排是複雜且不可避免，所以在探究租稅競爭時，租稅規避也是一項重要的考量因素。因此本文以Lai (2006) 一文為基礎，建構一個具有利潤移轉效果的國際租稅競爭模型，分別為Cournot數量競爭與Bertrand價格競爭，來探討廠商租稅規避效果對國際租稅競爭導致公共財提供量不足的影響問題。 本文章有幾點發現：Cournot 數量競爭下，避稅效果會強化稅基、稅收效果，和利潤移轉效果，加劇公共財提供數量不足的問題。而Bertrand價格競爭下，避稅效果同樣會使公共財提供量下降，但此模型下的利潤移轉效果對公共財影響為正向，使得公共財數量皆大於Cournot模型之下。此外，本文也探討眾多參數對政府最適決策的影響。 / The traditional literatures of tax competition, which include the rent shifting effect, ignore the impact of tax avoidance effect on public goods. However, the taxation arrangements between countries which firms face are complex and inevitable in this era of trade liberalization and internationalization. Therefore, when investigating tax competition, we should consider an important factor- tax avoidance. So, this paper is based on Lai (2006) to build an international tax competition model containing rent shifting effect. We will discuss the problem of insufficient public goods and how tax avoidance effect influence this question in Cournot competition and Bertrand competition. This conclusion shows that tax avoidance effect enhances tax-base effect, revenue effect and rent shifting effect in Cournot competition. In this condition, the issue of insufficient public goods will worsen. In Bertrand competition, tax avoidance effect will also make the quantity of public goods fall. But rent shifting effect in this model is so good for public goods that the quantity of public goods is larger than Cournot competition. Furthermore, this paper also uses software to test many parameters and finds the parameters how to influence government's optimal decision.