A resin film has through holes formed to extend through the thickness of the resin film. The through holes are pillar-shaped. An average density of the through holes is 1×106 to 1×1012 holes/cm2. An average diameter of the through holes is 1 to 310 nm. A degree of variability of the diameter of the through holes is 30% or less, the degree of variability of the diameter of the through holes obtained by dividing a standard deviation of the diameter of the through holes by the average diameter of the through holes and multiplying the resulting value by 100.