The appearance and design quality of a social commerce website should be considered, especially its influence on purchase decision-making, as previous studies have shown a specific influence. Facebook is one of the famous social media that adopt social commerce concepts. Recently, social media that adopt social commerce is increasing, indicating there is more competitor for Facebook. This study aims to study the effects of social commerce design website quality on purchase decision-making stages with Facebook as the object. Usability, functionality, and sociability are the social commerce website design quality factors studied in this research. Meanwhile, product awareness, information search, product evaluation, product purchase, and post-purchase are five stages involved in this research. The model was tested with 415 Facebook users in Indonesia who experienced online purchasing. This study showed a significant influence of usability factor, functionality factor, and sociability factor of Facebook towards product awareness, information search, product evaluation, product purchase, and post-purchase. The result of this study implies that Facebook should design a better usability, functionality, and sociability factors to enhance purchase decision- making stages. Also, online merchants on Facebook should formulate strategies to utilize design features provided by Facebook to better address customers' desires.