Recently, in the most of middle and small industries in Japan, they are facing extra-small amounts and extra-varieties in their products.In those cases, it is impossible to have enough background data for administration and/or scheduling software.Indeed, those data are extremely important for quick response to their customers order, and which are going to make competitive power to the opponents.In this study, we are going to propose estimation of production preparation time for each set-up for each machine by using Data Envelopment Analysis (DEA).Once we grasp production preparation time, we can grasp daily production ability for each machine.Moreover, once we grasp production abilities of machines in the factory, we can estimate total amount of products, and we can improve the accuracy of scheduling.So, it is very basic information that all administrator would like to grasp as precisely as possible.In this study, we use reliable data from daily products report in the Maruzen Industry.We have asked each employee to report direct production time, total production preparation time, total amount of products, total working times and a number of set-ups that they have done on daily base.However, we examined them and found the last three data are reliable.So, we have proposed a method to estimate production preparation time by using these three data.We have also used first two data to validate the effectiveness of the proposed method.Usually, if the number of set-ups raise, amount of total product reduces.Therefore, there are decline lines between these two data.We would like to estimate proper line trying to get rid of exceptional data from daily report.For that purpose, we use extended CCR model in Data Envelopment Analysis.Coefficient of this decline line means the estimated reduced amount of product for each set-up Then, we have reliable data reported as total number of set-ups for each day.Thus, we can estimate expected amount of products if there were no set-ups for daily basis.Once we divide this value with total amount of working time, we can estimate production speed per unit time.If we divide total amount of product by this estimated product speed, we can estimate true working time, and also we can estimate preparation time.Without any doubt, They are different from reported value.In this paper, we are going to examine about the difference and going to show the validation of the proposed method with these examinations.