Purgatory is the place, condition or process in which the souls of the dead suffer because of the bad things the y did when they were alive, so they became pure enough to go to heaven. Catholicism is the opinion, belief or doctrines taught by the Catholic Church. It is a church that covers the whole world, a collection of believers from all nations. Precisely, Roman Catholicism means a church that began in Rome, but has spread throughout the world. Purifying or what is called Purgatory in English is the doctrine of the Catholic Church, which means that Catholics are obliged to believe it. However, most Catholics in Indonesia are unsure about the status of their doctrine, and many even wonder what Purgatory is. From this background, this study aims to analyze the nature of the concept of Purgatory in Catholicism, and other Christian groups that oppose the doctrine. This type of research is qualitative research. To collect data relating to the problem under study, the researcher uses documentary techniques. Then the researcher tries to analyze the existence of Purgatory as a concept in Catholicism which is examined through data using descriptive analysis methods. From this study the researcher concludes, that based on the written Scriptures, Purgatory is a teaching in Catholic Christianity where Christians must perform the sacraments which have become the tradition of every church. The concept of Purgatory in Catholicism is where we can help the souls in Purgatory with prayers, especially by carrying out the sacraments taught by the church. But there arose the two biggest branches of Protestant reform, the Lutheran and Calvanis, which refused this. This is because there is no biblical basis in Christian teaching, nor is it written explicitly. Thus, this teaching is contrary to their theological concept of salvation. According to him that with the concept of Christ’s death and resurrection, Christians have been saved, then for what else is Purgatory as a way to go to achieve salvation. It is different from the teachings of the Catholic Church which believes that sanctification has lasted since still living in the world, such as through penance, but not apart from Purgatory which finally united with God. This is different from the Protestant belief, that sin was redeemed by Christ’s sacrifice, then Christians must undergo (purification) which lasts as long as they live in the world as a real sign of their repentance. After conducting this research, the researcher acknowledges that this research is still far from perfection, so the researcher expects the next researchers to examine this problem and compare it with the thoughts or understandings of other religious owners.Purgatory is the place, condition or process in which the souls of the dead suffer because of the bad things the y did when they were alive, so they became pure enough to go to heaven. Catholicism is the opinion, belief or doctrines taught by the Catholic Church. It is a church that covers the whole world, a collection of believers from all nations. Precisely, Roman Catholicism means a church that began in Rome, but has spread throughout the world. Purifying or what is called Purgatory in English is the doctrine of the Catholic Church, which means that Catholics are obliged to believe it. However, most Catholics in Indonesia are unsure about the status of their doctrine, and many even wonder what Purgatory is. From this background, this study aims to analyze the nature of the concept of Purgatory in Catholicism, and other Christian groups that oppose the doctrine. This type of research is qualitative research. To collect data relating to the problem under study, the researcher uses documentary techniques. Then the researcher tries to analyze the existence of Purgatory as a concept in Catholicism which is examined through data using descriptive analysis methods. From this study the researcher concludes, that based on the written Scriptures, Purgatory is a teaching in Catholic Christianity where Christians must perform the sacraments which have become the tradition of every church. The concept of Purgatory in Catholicism is where we can help the souls in Purgatory with prayers, especially by carrying out the sacraments taught by the church. But there arose the two biggest branches of Protestant reform, the Lutheran and Calvanis, which refused this. This is because there is no biblical basis in Christian teaching, nor is it written explicitly. Thus, this teaching is contrary to their theological concept of salvation. According to him that with the concept of Christ’s death and resurrection, Christians have been saved, then for what else is Purgatory as a way to go to achieve salvation. It is different from the teachings of the Catholic Church which believes that sanctification has lasted since still living in the world, such as through penance, but not apart from Purgatory which finally united with God. This is different from the Protestant belief, that sin was redeemed by Christ’s sacrifice, then Christians must undergo (purification) which lasts as long as they live in the world as a real sign of their repentance. After conducting this research, the researcher acknowledges that this research is still far from perfection, so the researcher expects the next researchers to examine this problem and compare it with the thoughts or understandings of other religious owners.