Provided is a battery comprising a separator comprising inorganic particles for preventing a short-circuit, wherein the inorganic particles are not removed readily from the separator. This battery is characterized by comprising a separator comprising a base material resin having voids and an inorganic particle having a surface (A) facing the void and a surface (B) in contact with the resin, wherein the length of the surface (A) is 50% or more of the length of the outer periphery of the particle in a cross-sectional SEM photograph of the separator.