The purpose of the study was to improve of performance for Magnetic Resonance Imaging (MRI) examination in the department of radiology. It was performed DMAIC (Define, Measure, Analyze, Improve, and Control). In the stage of definition, The fifth kinds of CTQ (critical to quality) by the kindness, the waiting time, the examination explanation, the waiting time and the waiting environment were selected by voice of customer. In the stage of measurement, the performed examinations and the reservation waiting time were measured each 1.77 and 1.69 sigma. In the stage of analysis, the potential key causes were determined the limited working hours and the difference of examination time of various entries. In the stage of improvement, MRI were performed with the operating system of 24 hours examination and the optimization of the difference of examination time by among of 30 minutes, 40 minutes, 50 minutes. Finally, the number of examinations and reserved waiting days were measured by each 3.17 and 1.71 sigma in the control stage.