Act against the law is an act that not only violates the rules and provisions of the law, but also conflicts with the subjective rights of others, as well as the principles that apply in society, which as a result of the act causes harm to others. An act can be said to be against the law, if it fulfills the elements as stipulated in Article 1365 of the Civil Code, namely: (a) an act, (b) the act is against the law, (c) an error, (d) a loss, and (e) there is a causal relationship (causality) between the unlawful act and the resulting loss. Act against the law can occur anywhere and anytime, starting from a small scope such as the environment around us, to a larger and global area. In 2016, there was a case where Chahyono Kusumo (Plaintiff) sued So Sie Gwan (Defendant) on the basis of unlawful acts. The lawsuit was filed because the Plaintiff suffered severe damage to his house and found material and immaterial losses as a result of the construction of the house carried out by the Defendant. The problem in this research is how to fulfill the elements of unlawful acts committed by the Defendant in Decision Number: 1009/Pdt.G/2016/PN.Sby and how to be responsible for the compensation. In this study, the method used by the author is a normative legal research method with qualitative data analysis methods. This study uses secondary data obtained through library research, after which, the data is collected and analyzed using an approach to legal principles and a case study approach. From the results of the study, it can be concluded that the Defendant is legally declared to have committed an unlawful act because it has fulfilled the elements in Article 1365 of the Civil Code, and is sentenced to compensate the Plaintiff for material losses.