本文主要比較天主教與佛教的懺悔思想與實踐。懺悔是行為主體對犯錯的罪惡意識的表達，是世界性宗教的共通特性之一。在宗教上的罪主要是違反戒律，可能是倫理上的惡或是信理的違背，不同宗教間有些共通性與獨特性。佛教與天主教有很不一樣的宇宙觀、神觀與戒律，會影響罪惡感的形成，進而影響懺悔思想與實踐。天主教的創世神觀，觸犯與懺悔的對象主要是天主，也只有祂有赦罪的權柄，透過教會的聖職人員，藉由懺悔聖事，罪人重新與天主、與教會和好。佛教認為世界是因緣而生，在達涅槃之前，生命不斷輪迴，因我執、法執，違背佛法、戒律，而產生煩惱與業障。為減輕業障，需及時懺悔，懺悔的對象從佛陀到諸佛，也因所守戒律、犯錯情況以及時空不同而有不同的懺悔作法。
兩個宗教間的共通性與獨特性也因比較而呈現。主要的共通點有：承襲原有宗教的部分觀念與作法，以戒律作為懺悔的重要依據，懺悔與修行的配合，從公開懺悔、私下懺悔到個人懺悔的趨勢，懺悔的行為廣泛存在各種宗教儀軌中，懷有希望與精進的宗教體驗，以及邁向超越或解脫，獲享永福的企盼等。主要的差異產生於赦罪權柄、重大過犯得赦方式是否唯一、懺悔儀式的通用性、告明要求與否、補贖或迴向、入華後懺悔方法的創新，以及生命體悟等方面。

The study is to compare the thought and praxis of repentance between Catholicism and Buddhism. Repentance, one of the areas common to world religions, is an expression of guilty consciousness of criminal subject. Religious sins occur mainly because of offending commandments or precepts, morally misbehaving or violating doctrines. There are similarity and uniqueness among religions. Catholicism and Buddhism have different concepts about universe, as well as God and precepts which affect the formation of sense of guilt and then affect the thought and praxis of repentance. For Catholicism, God is the Creator of the world, and He is the object penitents offend and show repentance to. And only God Himself can forgive penitents. Through the priests and the Sacrament of Repentance, penitents reconcile with God and the Church. For Buddhism, the world was formed through cause and condition, and the lives will be reincarnated. Because of self-attachment (ātma-grāha), Dharma-attachment or violating the precepts, there occur vexations and karma. To reduce karma, penitents need to repent in time. The penitents show repentance to Buddha or buddhas. According to the precepts obeyed and different situations, various repentant methods are performed.
The similarity and uniqueness of repentance between the two religions are presented after comparison. The main similarities of repentant thought and praxis are as follows: parts of them are originated with the former religion, precepts are their important base, they match for spiritual exercise, there exists a trend of changes from public to private repentance in the historical development, there are practices in plural rituals, and religious experiences with hope and progress to gain eternal happiness. The main differences are the authority to forgive, one or plural ways to forgive great or mortal sins, the generality of repentant ritual, the necessity of confession, satisfaction or parināma, the innovation of repentant performance in China, and the insight of life.