P PT Waskita Beton, a company in manufacturing. The product under study was Fullslab type 2B. The aim of this research is to minimize defective products based on the six sigma method. The stages are carried out with the Six sigma method such as DMAIC. The define stage, uses the SIPOC diagram to find out information between suppliers to customers, and makes a critical to quality matrix, the measure stage to determine the control chart whether the limit is running stably or not, then calculating the DPMO and the sigma level, the Analyze stage to analyze the cause of the problem using the diagram pareto, fishbone diagram, and FMEA, the upgrade stage to provide a proposed improvement using the 5W1H and DOE, the control stage comparing the DPMO before and after the repair. The sigma level value on the p map is 3.73 sigma and the cpk value on the variable map is 0.78. In the FMEA table, the defects in shrinkage cracks due to poor quality splits, porous defects due to measurement errors of the composition of the concrete mixture, defects in milling due to lack of maintenance, and defects in compressive strength not according to quality due to the composition of the mixture not according to quality. The conclusion obtained from the proposed repair of shrinkage crack defects using an incoming material inspection form, porous defects using a digital electronic weighing scale, compact defects using a form regarding molding treatment, and defects resulting from compressive strength not according to quality using DOE and plot intervals, good composition on factors the mixture of sand and split is 1350kg, the cement factor is 432kg, and the water factor is 215L.