POROUS POLYIMIDE FILM, SECONDARY BATTERY SEPARATOR, AND SECONDARY BATTERY

A porous polyimide film has plural pores, in which an average flattening of the plural pores is within a range of 0.1 to 0.7, a coefficient of variation of a distance between adjacent pores is within a range of 0.10 to 0.40, and a front surface and aback surface communicate with each other through the plural pores.