As an object to provide a lithium-ion supercapacitor having a high energy density and a high power density, capable of being charged and discharged many times, and having a long product life, there is provided a lithium-ion supercapacitor using a graphene/CNT composite electrode, the lithium-ion supercapacitor including: an anode; a cathode that is arranged to be separated from the anode; and a lithium ion electrolytic solution that fills in a space between the anode and the cathode, wherein either or both of the cathode and the anode are formed by a graphene/CNT composite, and a CNT concentration in the graphene/CNT composite is 17 wt % or more and 33 wt % or less.