The present study aims to enhance the performance of the rice grain-milling machines by using an attached primary cleaning-unit.  The performance of the developed rice grain-milling machine was studied in terms of four different sieve shapes “CSS" of the attached primary cleaning unit (“A", “B", “C" and “D") with four different feeding rates (1.00, 1.25, 1.50 and 1.75 Mg/h) and four different primary cleaning sieve “PCS" speeds (310, 360, 420 and 470 rpm). The machine performance was depended on measuring machine productivity, machine efficiency, cleaning efficiency, total grain losses, required power, energy requirements and both operational and criterion costs. Results indicated that the best performance was yielded with the use of primary cleaning unit sieve shape “D" side by side with adjusting the feeding rate at 1.25 Mg/h and “PCS" speed at 360 rpm. Under these conditions values of machine productivity, machine and cleaning efficiencies were 1.20 Mg/h, 94.80 % and 96.90 % respectively. Meanwhile, the required power and energy requirements were 17.0 kW and 20.53kWh/Mg respectively. Finally, minimum operational and criterion costs were 43.18 and 94.52 LE/Mg, respectively.