We have been developing a laser-Compton X-ray source using an optical enhancement cavity. We have studied 1um pulse laser storage in optical cavity and use for the experiments. Usage of 10 um laser for optical enhancement cavity will increase the X-ray energy region of one laser-Compton X-ray source, so that we decided to develop the optical cavity for CO2 laser. We have designed external optical cavity for CO2 laser commercially available optics and verified the enhancement of CO2 laser in external enhancement optical cavity, and measured fundamental parameters such as finesse, matching efficiency, and enhancement factor. We have already achieved 475 of finesse, 43 of enhancement, and tested non-planer cavity, which storages two circular polarization separately. In this conference, we will report the design and experimental results of CO2 laser storage cavity and also some future prospects.