The purpose of this study was to measure and analyse the economic efficiency, and to identify the main factor behind economic efficiency of sorghum and millet for small scale farmers in traditional rainfed sector in North Kordofan State. Primary data is collected using structured questionnaire for a sample of 205 farmers from four localities namely (Sheikan, Umrwaba, Elnuhoud, and Elkhowi). Stochastic frontier approach (cost function) was used to analyse economic efficiency and descriptive statistics were used to analyse socio-economic characteristics of farmers. The results of stochastic frontier cost function revealed that the estimated economic efficiency of the sorghum and millet farmers obtained was found the mean economic efficiency to be 39% and 15%, respectively. The economic efficiency is very weak, because most parameters and inefficiency effect factor found to be not significant, these determinants may give a clear picture of farmers that could be targeted in order to increase efficiency