The main aim of the article is to focus on the undertaking as an object of the legal relations. The author of the article tries to analyse the essence of the undertaking and the structure of undertaking from the legal point of view. The author critically looks at opinions of legal experts according to which is the undertaking the collective thing. Moreover, he analyses two other theories which deal with the undertaking as an object of the legal relations. The first theory is the theory of an undertaking as another property value and the second is the theory of undertaking as an object called sui generis.