Abstract: This research aims to analyze the factors that cause the insignificant development of sharia banking performance in Indonesia. This research focuses on identifying practices that are not purely sharia as the causal factors that hinder the development of sharia banking. The population in this research is Sharia Commercial Banks (BUS) registered with the Financial Services Authority (OJK) in the 2014-2018 period. The data obtained was analyzed using multiple regression with panel data. The results of this research indicate that murabahah financing and profits from transactions denominated in foreign currency have a negative effect on the performance of sharia banking. Financingmurabahaproven to increase Non-Performing Financing (NPF), in addition, transactions denominated in foreign currency are proven to reduce Return on Assets (ROA), as well as increase Operating Expenses, Operating Income (BOPO) and NPF of sharia banking. Meanwhile, non-halal income has no effect on sharia banking performance. The implication of this research is that sharia banking must improve operational practices that are not purely sharia to make them pure sharia. The two regulators, namely the OJK and the government, create a more conducive environment so that sharia banking is able to implement operational practices in accordance with sharia principles.Keywords: financial performance, sharia banking, impure sharia practicesIntroductionSharia banking is a representation of Islamic economic practices in Indonesia. Sharia banking is expected to provide a new color in the financial sector that is significantly different from conventional banking. However, in practice, sharia banking has notbeen able to create significant uniqueness which is ultimately considered to be one of the causes of the lack of development of sharia banking itself. Sharia banking is considered to have had stagnant development since its presence in Indonesia, even after the number of BUS became 14, the performance of sharia banking has not yet shown encouraging performance. This can be seen in the development of market share in the last 8 years, only ranging from 3.98% to 5.89% (Sharia Financial Development Report 2018;LPPM Report, 2018). Over the last 8 years the sharia banking market share has only grown by 1.8% with several declines. However, this growth in market share does not solely come from business growth but is