Microporous films of the semicrystalline polymer resin according to the present invention are obtained by stretching semicrystalline polymer resin sheets extruded through a die by the phase separation between a semicrystalline polymer resin and a diluent, of which cross-section is comprised of a pore region and a non-crystalline region which is in the main matrix phase and is a swelling region swelled by the diluent, and extracting the diluent. The pore region has irregular sizes and shapes, has an average diameter of 0.01 (m to 2 (m, is connected in three dimensions, penetrates the thickness of the sheet, has gas permeability, has a volume ratio with respect to the volume of the entire resin composition of 10% to 40%. The swelled non-crystalline region has a swelling ratio of 200% or greater and is a region making minute cells of which average diameter is 0.01 (m to 1 (m as the region is split and cells are formed during the process of stretching. Thus manufactured microporous films are characterized by having a gas permeability of 1.3×10−5 Darcy or greater as well as *a puncture strength of 0.1 N/mm or greater even without tearing or breaking of the pores during the process of stretching.