The present invention relates to a composite solid electrolyte comprising zeolite and a fluorine-based lithium salt, and a lithium secondary battery using same. In the composite solid electrolyte according to the present invention, the formation of lithium dendrites is dramatically reduced by optimizing the concentration of fluorine-based lithium salt in a composite solid electrolyte containing zeolite, thus making it possible to achieve a composite solid electrolyte and a lithium secondary battery comprising same in which very good electrochemical characteristics are exhibited even after long-term charging and discharging.
