As customer's needs change rapidly in recent days, the evaluation scale about service quality is changing against the variation of the customer's needs. It is fact that the need of change which established evaluation ways about service quality rise more and more. 6-Sigma activity, called "most innovative management strategy in 20th Century", have many problems apply to service company. The important one between these problems is the problem about Critical To Quality(CTQ) Selection caused from the absence of more precise evaluation system. The objective of this study is the development of methodology for CTQ selection coincide to service company. It is the basic logic that the way to regard MOT mainly effects about total customer satisfaction index(CSI) as CTQ, after the development of the evaluation system based on MOT with customers. Also, the study focused on the case of department store progress to exhibit the reasonableness of this logic.