Activated carbon used for an electrochemical element in which when W1 and W2 satisfy 1.0 nm ¤ W1 < W2 ¤ 2.0 nm, a total pore volume of the activated carbon in which a slit width obtained by an MP method is W1 or more and W2 or less is 15% or more of a to...

A fibrous active carbon having pores in the surface, wherein the pore diameter falls within a range of 0.1 to 200 nm, and, the active carbon is in the form of a fiber, and has a fiber diameter of less than 1000 nm or less.