This paper proposes a model to evaluate the maturity level of quality management system of semiconductor companies. We classify the maturity level into 5 stages: initial, forming, storming, performing and mature stage. To evaluate the maturity level, 10 categories of quality management with 3 or 4 factors each are identified: management leadership, strategy planning, business process improvement, customer & market, corporate quality culture, product design & development, mfg. process control, human resource, supplier control, implementation performance. Scoring 224 items in total, the value of each factor is evaluated by weighted average of those items. Maturity level is appraised by rating the sum of scores of 10 categories that are obtained by summing up the values of those 3 or 4 factors. Values of weights and criteria of rating maturity level are determined by analyzing 7 companies. This study shows the actual evaluate results of some companies.