Electrode active material for capacitor, and capacitor using said electrode active material

An electrode active material for a capacitor, the electrode active material containing a porous carbon material, wherein: the BET specific surface area of the porous carbon material is 800 m 2 /g or more; the X-ray diffraction image of the porous carbon material obtained by using Cukα rays has a peak (P k ) at 2θ= 40 to 50 degrees; P k contains a peak (P d111 ) component belonging to the (111) plane of a diamond crystal; and when the X-ray diffraction image has a peak (P G002 ) belonging to the (002) plane of graphite, the ratio of the intensity (I G002 ) of P G002 relative to the intensity (I k ) of P k is 3.0 or less when I G002 /I k .