本文以追尋租稅正義為題，探討從憲法第7條規定之平等原則，一直延伸到稅捐法上量能課稅原則的過程及路徑。先從我國規範、釋憲實務，以及學說中關於平等權或平等原則的理解開始，一直討論到美式與德式關於平等原則之審查步驟的差異，認為美式所注重之分類標準，其實應該是德式之平等原則審查步驟中，關於事物之可比較性基礎的前提要件，故若欲討論稅捐規範是否合乎租稅正義，亦須先尋求稅捐負擔分配的分類標準。找尋分類標準，應先斟酌客觀受規範之事物的本質，與規範亦即分類適用者之主觀目的，兩者綜合而作決定。由於稅捐是國民為滿足國家之財政需要而為的金錢給付，故稅捐屬於國民彼此間之負擔分配的概念，追尋租稅正義即須在分配正義之概念下進行。從分配正義觀點來看，幾種可能作為稅捐負擔分配之標準者，包括每人均等的人頭稅、按照個人受益程度而分配之量益稅，與按照個人之負擔能力而分配的量能稅，後者即為稅捐法之量能課稅原則。本文採取多數國家在稅捐法制上所採用之量能課稅原則，並且討論量能課稅原則，在德國與在我國之釋憲實務上的發展。最後則討論稅捐優惠規範，應具備之審查標準，本文認為，至少應為美式的中度或嚴格審查標準，或者是採取德式的合於比例之平等原則的審查密度。

In this article, with the issues to pursue for justice of taxation, researches the path from general principle of equality based on the Article 7 of the Constitution extends to the ability-to-pay principle in tax law. Beginning with the specifications, constitutional interpretations and doctrine or principle of equality of rights, have been discussing the differences between American and German Praxis on the principle of equality. In compare to the steps for review of unconstitutional law in American focus on the classification criteria, in Germany are on the other hand to reviewing the comparability requirements based on the premise, if there are reasonable lawmaker’s decisions to justify. Since taxes are to meet the financial needs of countries and for the inland people to payment of money, it belongs to the distribution of burden of taxes between each individual. To pursue tax justice shall proceed under the concept of distributive justice. From the standpoint of distributive justice, several possibilities as a standard for distribution of the burden of those taxes, including equal per head tax, equal in accordance with the degree of personal benefit and equal in accordance with the amount of the individual's ability to pay. In this paper is the ability to pay principle considered as fundamental principle for tax laws. Finally, the discussion of preferential taxes, this paper argues, it should be examined at least moderate or strict American standard of review, or take German synthetic review based on the so called new model of principle of equality.