Indonesia’s banking sector is expected to improve the performance management productivity positive direction (in other words the emphasis on earnings quality and performance should be improved), and making it into the (Association of Southeast Asia Nations) ASEAN free market in 2020 and became the largest bank in ASEAN.The aim of this study are to determine the factors that affect income smoothing on the National Private Commercial Foreign Exchange Banks that listed in Indonesia Stock Exchange (IDX). Variables used in this study are the firm size, profitability and financial leverage. Eckel Index (1981) was used to measure income smoothing, where net profit after tax as income smoothing object.The sample was taken by random sampling of 10 private foreign exchange national banks that listed in Indonesia Stock Exchange (IDX) during the years 1/1/2009 to 31/12/2013 with a sub-sample of 50 financial reports. Testing is done through panel data analysis technique with simultaneous test (F test) and partial test (t test) was used to identify factors that affect income smoothing.The results showed that income smoothing is done by most of the National Private Commercial Foreign Exchange Bank which listed on the Indonesia Stock Exchange (IDX). The test results result are variable size of the company, profitability and financial leverage simultaneously significant effect on income smoothing. Partial test results are that the variable size of the company, profitability and leverage financial has effect on income smoothing.