The purpose of this study is to analyze and describe the implementation of the just in time in the production process of the garments on the Subsidiary Company PAN 12 PT. Pan Brothers Tbk in Boyolali, Central Java and to know how the implementation of the just in time in relation to improving the effectiveness of the production. To find out how much the company achieved production effectiveness, in this study used measurement method by using the calculation of the Manufacturing Cycle Effectiveness (MCE) by dividing the non value added activities and value added activities, from the calculation of the MCE can be the measurement of the effectiveness of the company where the company has a value of 100% means the MCE has the ideal production effectiveness, while less than 100% then needed improvement. The result of this study, the calculation of the Manufacturing Cycle Effectiveness (MCE) generated in the implementation of the just in time of 66,19%. From that result, companies can make improvements by reducing or eliminating non value added activities to increase the value of the MCE, with the result that effectiveness of production can be achieved. Based on the results of the analysis there is a difference between the Manufacturing Cycle Effectiveness (MCE) between in advance of improvements of 66.19% and following improvement of 79,19%. Improvement attempts by reducing or eliminating non value added activities capable of improving the Manufacturing Cycle Effectiveness (MCE) of 13% (79,19%-66,19%) than in advance of improvements in the implementation of the just in time.