The process capability index Cpm is known as one of useful quality measures of process. Then, the Cpmcontrol chart has been proposedfor monitoring the process condition, and the economical operation of the Cpm control chart has been investigated. On the other hand, in sampling inspection, it is well known that double sampling plan can reduce average sampling number in comparison with single sampling plan. In this study, for the purpose of reducing the expected operating cost in the Cpm control chart, we address the double sampling Cpm control chart incorporating the feature that the judgment rule of the 2nd sampling stage is independent of the data record of the 1st sampling stage. The design algorithm for the addressed double sampling Cpm control chart is constructed. Through numerical comparison, it is verified that the proposed double sampling Cpm control chart has advantage in the expected operating cost against the existing single sampling Cpm control chart.